enhance(#3873): the STATE.md schema — one owner, generated artifacts (#3880)

* test(#3873): failing-first locale parity, plus tripwires for what must not move

Pins ADR-3473 §8.8 at the artifact a reader actually sees. The English STATE.md
reference carries a Status lifecycle section that is missing from all four
translations — the section documenting the status enum whose clobbering is
#3853. The test derives the heading set rather than hard-coding the missing
one, and names the locale and the heading when it fails.

Two tripwires that must pass today and after. The field-drift guard still
catches a re-derived fallback ladder: §8.8 instructs deleting that script, and
that instruction rests on a wrong premise about what it guards, so the test
stops a future reader from deleting it on the ADR's word. And last_activity's
label resolution is pinned to what ships today, because it is declared in one
of the two tables this phase consolidates and not the other — the
consolidation must not silently pick a side.

The locale test buckets under docs rather than state, which is what it tests;
that bucket is allowlisted with justification rather than folded into an
unrelated docs suite. It reads only markdown, so it carries no allow-test-rule
marker — a marker there would suppress nothing and would grow the unverified
pool against its ceiling.

Refs #3873

* feat(#3873): one schema owns the STATE.md key set, three tables become projections

ADR-3473 §8.8. The key set was declared in four places that had to agree by
hand and already did not: FIELD_CLASSIFICATION, FRONTMATTER_BODY_SOURCE,
FRONTMATTER_KEY_TO_BODY_LABEL and buildStateFrontmatter's emit behavior. One
frozen null-prototype schema now declares each key's type, enum, cardinality,
source, preservation, body source, body label, accepted parse shapes and
whether it is emitted unconditionally; the three tables are derived from it at
module load.

The projections are byte-identical to the literals they replace, key order
included, and the parity tests compare against verbatim copies of today's
tables rather than re-deriving both sides from the schema — a parity test fed
from one source proves nothing, which is how a consolidation ships a changed
policy under a green test.

last_activity was the live disagreement: present in one table, absent from the
other. The schema declares what ships today rather than the tidier answer, and
a test pins it.

The schema is a leaf module and owns the four field-policy types, re-exported
from state-transition so existing importers are untouched — the same split
health-diagnostic-types made to break a CJS require cycle.

Refs #3873

* feat(#3873): generate the schema-derived regions, parity-check the prose tables

ADR-3473 §8.8's generator half. gen-state-md-docs.cjs owns marked regions in
the shipped template and all five reference docs, follows gen-features.cjs's
fail-closed contract, and is wired into regen:derived and lint:generated-sync.

The Status lifecycle section was missing from all four translations — the
section documenting the status enum behind #3853 — and is now generated into
every locale. Field cardinality is a new generated table: pure schema data,
no prose, so nothing to lose.

The Field-reference and Status-values tables are parity-CHECKED rather than
generated. Their Purpose, When-populated and Matched-text columns are
genuinely hand-translated per locale, and §8.8 itself says prose stays
hand-translated; generating them from an English registry would overwrite four
locales' translations on every write. The row set is checked against the schema
instead, so a key added to one and not the other fails, which is what field
drift actually means. Building that check found last_activity_desc
undocumented in all five tables.

Three keys the docs describe are absent from the schema — active_phase,
next_action, next_phases. They are grandfathered by name, not by wildcard, so a
fourth fails: a declared gap with a forcing function rather than a silent one.

Refs #3873

* fix(#3873): declare what the parsers do, and close the shape-parity gap

Two declarations in the new schema described intended behavior rather than
actual — the defect class this epic exists to end, committed inside the epic.
Both were caught by executing the parsers instead of reading their docstrings.

current_plan.acceptedShapes claimed ['N', 'N of M']. Standalone, the hybrid
shape errors; the path that looks like support is parseInt truncating '2 of 5'
to 2 and discarding the rest. Narrowed to ['N']. The parser is deliberately NOT
fixed here: that is #3784 and PR #3791 is already doing it. When #3791 lands
this row must widen, and the shape test will go red until it does — the schema
and the parser cannot drift apart quietly, which is what §8.8's checked-not-
generated rule is for.

STATUS_LIFECYCLE_ENUM claimed to be the closed set status can hold.
normalizeStateStatus passes unrecognized prose through unchanged, so it is not
closed at runtime. The seven members are the canonical values it maps onto; the
docstring now says that and the test asserts the real lenient contract.

Closes the acceptance item that a test asserts the parsers accept exactly the
declared shapes: the check is table-driven over every row carrying
acceptedShapes, guarded against passing vacuously on an empty set, and fails
loudly if a future row has no registered driver. Adds the unwired-label throw
and the fast-check property that every projection agrees with its schema row.

Refs #3873

* fix(#3873): keep the shipped template's frontmatter first, and make row 27 able to fail

The remote matrix caught 12 failures with one cause. Making the template's
frontmatter a generated region wrapped it in its own yaml fence ahead of the
markdown fence, so extractFileTemplate and readShippedStateTemplateBody — which
both match the single markdown block — found the heading first, not the
frontmatter. That breaks the contract every new project's STATE.md is created
from: bug #21 and epic #1969 B8 pin that the File Template block starts with
frontmatter and carries gsd_state_version.

The markers now sit inside the single markdown fence, so the fence opens before
the frontmatter and the region still ends ahead of the heading. Same layout as
before this phase, with markers embedded rather than a second fence.

Row 27 existed to catch exactly this and did not, because it was writer-seeded:
it asserted against the generator's own output shape, so it passed on the broken
template. It now parses the fence the way production does and was verified to
fail against the broken shape before being trusted against the fixed one. A test
that would not have caught the bug it exists to prevent is worse than no test.

The emitted-attribution failure was separate and the fragment was the wrong
remedy: gsd-core/templates/state.md self-attributes under a verbatim-copy
identity rule, so a diff touching it needs no acknowledgment. Fragment deleted
rather than left explaining nothing.

Refs #3873

* docs(#3873): how to change the STATE.md schema

The phase gate was right and my docs artifact was wrong. I listed
lint:generated-sync as the second enablement step, which is a verification
command dressed as one, and then claimed a one-step sequence owed no how-to.

The real sequence is build:lib then regen:derived, and the ordering is a trap:
the generator reads the COMPILED schema, so regenerating before building
regenerates against the previous schema and commits artifacts that look
plausible while disagreeing with the code just written. A reference table
cannot carry an ordering dependency; that is what the how-to test is for.

The page covers adding, changing and removing a key, every reason code the
check emits and what to do about each, what is generated versus hand-translated
and why the two prose-bearing tables are parity-checked instead of generated,
adding a language, and the three grandfathered keys. Indexed from docs/README.md.

Refs #3873

* chore(#3873): backfill changeset PR number

---------

Co-authored-by: sim <sim@local>

src/state-transition.cts

@@ -22,6 +22,10 @@ import { tokenizeHeadings } from './markdown-sectionizer.cjs';
 import type { HeadingToken } from './markdown-sectionizer.cjs';
 import { deriveProgressFromRoadmap, clampPercent } from './phase-lifecycle.cjs';
 import { escapeRegex } from './pattern.cjs';
+// eslint-disable-next-line @typescript-eslint/no-require-imports
+import stateMdSchemaMod = require('./state-md-schema.cjs');
+const { STATE_FIELD_SCHEMA } = stateMdSchemaMod;
+type StateFieldSchema = stateMdSchemaMod.StateFieldSchema;
 
 const { extractFrontmatter, reconstructFrontmatter, stripFrontmatter } = frontmatter;
 
@@ -40,33 +44,21 @@ const STOP_H2_PLUS = (lv: number): boolean => lv >= 2;
 // the collapsed-enum shape as a substrate defect that wouldn't survive
 // Phases 2–7.
 
-export type FieldSource =
-  | 'body' // value is derived from a body field (Phase:, Status:, etc.)
-  | 'disk' // value is derived from a disk scan (.planning/phases/* counts)
-  | 'external' // value is derived from an external file (ROADMAP.md milestone)
-  | 'curated' // value is set by humans/tools; preserve unless explicitly overwritten
-  | 'free'; // caller's word is law (no preservation)
-
-export type FieldPreservation =
-  | 'derive' // always re-derive from source
-  | 'preserve-when-unchanged' // #1230 delta heuristic: keep existing if body source field unchanged
-  | 'preserve-always' // never overwrite unless the caller explicitly names this field
-  | 'preserve-if-placeholder'; // overwrite only when derived value is a known placeholder (#948)
-// ADR-3408 §8.6 amendment: 'clear' was deleted (no row used it, no executor
-// existed) rather than implemented — Speculative Generality, a policy
-// invented for a need that never arrived.
-
 /**
- * ADR-3408 Decision 1 (Greenspun's Tenth Rule): guards and merge strategies
- * are named members of a CLOSED vocabulary, never an open predicate slot. The
- * table has already accreted five times (`preserve-always` #1743/#1695,
- * `preserve-if-placeholder` #948/#2135, `state_head` #2573, `deriveProgressKeys`
- * #2440, `bodyDeltas` #3258) — an open per-row predicate is what would turn
- * this table into an interpreter. Adding a member to either union below is an
- * amendment to ADR-3408, not a table edit.
+ * #3873 (ADR-3473 §8.8): the four closed vocabularies below moved to
+ * `src/state-md-schema.cts` — the leaf module `FIELD_CLASSIFICATION`'s
+ * projection is now derived from — and are re-exported here BY THE SAME NAME
+ * so no existing importer of this module needs to change (`state.cts`
+ * consumes them via `stateTransitionMod.FieldSource` etc., the namespace
+ * access pattern this module's plain `export type` already supported before
+ * this move). See `state-md-schema.cts` for the full ADR-3408 Decision 1
+ * ("Greenspun's Tenth Rule" — closed vocabulary, never an open predicate slot)
+ * docstring these four used to carry directly.
  */
-export type FieldGuard = 'non-sentinel-unknown';
-export type FieldMergeStrategy = 'progress-ratchet';
+export type FieldSource = stateMdSchemaMod.FieldSource;
+export type FieldPreservation = stateMdSchemaMod.FieldPreservation;
+export type FieldGuard = stateMdSchemaMod.FieldGuard;
+export type FieldMergeStrategy = stateMdSchemaMod.FieldMergeStrategy;
 
 export type FieldClassification = {
   source: FieldSource;
@@ -91,55 +83,30 @@ export type FieldClassification = {
  * (`FIELD_CLASSIFICATION['toString']` returns undefined, not the inherited
  * function). Use `getFieldClassification()` for lookups.
  */
+/**
+ * #3873 (ADR-3473 §8.8): PROJECTED from `STATE_FIELD_SCHEMA`
+ * (`src/state-md-schema.cts`) rather than hand-maintained here. Byte-identical
+ * to the pre-#3873 literal table — same 19 keys, same key ORDER (walks
+ * `Object.keys(STATE_FIELD_SCHEMA)` directly; see that module's row-order
+ * comment for why this is the one projection allowed to do that), same
+ * per-row shape (`{source, preservation, guard?, mergeStrategy?}`, in that
+ * key order, `guard`/`mergeStrategy` present only when the schema row carries
+ * them — never as an `undefined` own-property), same frozen null-prototype
+ * container. Pinned by `tests/state-transition.test.cjs`'s
+ * `fieldClassificationProjectionMatchesTodaysTable`, whose comparand is
+ * today's literal copied VERBATIM into the test (never re-derived from this
+ * schema — see that test's own docstring on why a self-referential parity
+ * test proves nothing).
+ */
 export const FIELD_CLASSIFICATION: Readonly<Record<string, FieldClassification>> = Object.freeze(
-  Object.assign(
-    Object.create(null) as Record<string, FieldClassification>,
-    {
-      // Schema
-      gsd_state_version: { source: 'free', preservation: 'derive' } as FieldClassification,
-
-      // Milestone (external — from ROADMAP.md)
-      milestone: { source: 'external', preservation: 'preserve-if-placeholder' } as FieldClassification,
-      milestone_name: { source: 'external', preservation: 'preserve-if-placeholder' } as FieldClassification,
-
-      // Phase / plan position (body-derived)
-      current_phase: { source: 'body', preservation: 'preserve-when-unchanged' } as FieldClassification,
-      // #1743, #1695. #3468: row corrected to match its long-standing behavior
-      // — was declared preserve-always, has always been delta-gated (only
-      // restores when the body `Phase:` source is unchanged this write).
-      current_phase_name: { source: 'curated', preservation: 'preserve-when-unchanged' } as FieldClassification,
-      current_plan: { source: 'body', preservation: 'preserve-when-unchanged' } as FieldClassification,
-
-      // Status / lifecycle (body-derived; #1230 delta heuristic applies)
-      // guard: the 'unknown' sentinel is the ONLY true executor-side guard in
-      // this table (stopped_at's `## Session` scoping is caller-side delta
-      // extraction, not an executor condition) — ADR-3408 Decision 1.
-      status: { source: 'body', preservation: 'preserve-when-unchanged', guard: 'non-sentinel-unknown' } as FieldClassification,
-      stopped_at: { source: 'body', preservation: 'preserve-when-unchanged' } as FieldClassification,
-      paused_at: { source: 'body', preservation: 'preserve-when-unchanged' } as FieldClassification,
-
-      // Activity log
-      last_updated: { source: 'free', preservation: 'derive' } as FieldClassification, // realClock.nowIso()
-      last_activity: { source: 'body', preservation: 'derive' } as FieldClassification, // always refresh on transition
-      last_activity_desc: { source: 'body', preservation: 'preserve-when-unchanged' } as FieldClassification,
-
-      // Commit provenance (#2573) — ambient git read, recomputed on every write,
-      // exactly like last_updated. Never preserved: a stale stamp would claim
-      // STATE.md was written against a commit it wasn't.
-      state_head: { source: 'free', preservation: 'derive' } as FieldClassification, // #2573
-
-      // Progress block (disk-derived, except the curated progress ratchet)
-      // mergeStrategy: 'progress-ratchet' — completed_plans/completed_phases
-      // only ever ratchet UP toward the derived value (#2969); everything
-      // else in the merge is either always-derived (#2440) or always-curated.
-      progress: { source: 'curated', preservation: 'preserve-always', mergeStrategy: 'progress-ratchet' } as FieldClassification, // #3242, #1446
-      'progress.total_phases': { source: 'disk', preservation: 'derive' } as FieldClassification,
-      'progress.completed_phases': { source: 'disk', preservation: 'derive' } as FieldClassification,
-      'progress.total_plans': { source: 'disk', preservation: 'derive' } as FieldClassification,
-      'progress.completed_plans': { source: 'disk', preservation: 'derive' } as FieldClassification,
-      'progress.percent': { source: 'disk', preservation: 'derive' } as FieldClassification,
-    } satisfies Record<string, FieldClassification>,
-  ),
+  Object.keys(STATE_FIELD_SCHEMA).reduce((acc, key) => {
+    const row: StateFieldSchema = STATE_FIELD_SCHEMA[key];
+    const projected: FieldClassification = { source: row.source, preservation: row.preservation };
+    if (row.guard !== undefined) projected.guard = row.guard;
+    if (row.mergeStrategy !== undefined) projected.mergeStrategy = row.mergeStrategy;
+    acc[key] = projected;
+    return acc;
+  }, Object.create(null) as Record<string, FieldClassification>),
 );
 
 /**
@@ -163,19 +130,36 @@ export const FIELD_CLASSIFICATION: Readonly<Record<string, FieldClassification>>
  * builder derives from disk, an external file, or the clock have no body source
  * and are deliberately ABSENT here rather than mapped to a lie.
  */
+/**
+ * #3873 (ADR-3473 §8.8): PROJECTED from `STATE_FIELD_SCHEMA`
+ * (`src/state-md-schema.cts`)'s `bodySource` field, in this EXPLICIT key
+ * order. This order is NOT `STATE_FIELD_SCHEMA`'s own row order filtered down
+ * to the body-sourced keys — the pre-#3873 literal already put `status`
+ * before `stopped_at`/`paused_at` here while `FRONTMATTER_KEY_TO_BODY_LABEL`
+ * (`src/state.cts`) put it AFTER them, i.e. the two pre-existing tables
+ * disagreed with each other's order too, and this projection must reproduce
+ * ITS table's order specifically. Byte-identical to the pre-#3873 literal —
+ * same 8 keys, same order, same frozen null-prototype container with frozen
+ * per-key arrays. Pinned by `tests/state-transition.test.cjs`'s
+ * `bodySourceProjectionMatchesTodaysTable`.
+ */
+const FRONTMATTER_BODY_SOURCE_KEY_ORDER = Object.freeze([
+  'current_phase',
+  'current_phase_name',
+  'current_plan',
+  'status',
+  'stopped_at',
+  'paused_at',
+  'last_activity',
+  'last_activity_desc',
+] as const);
+
 export const FRONTMATTER_BODY_SOURCE: Readonly<Record<string, readonly string[]>> = Object.freeze(
-  Object.assign(Object.create(null) as Record<string, readonly string[]>, {
-    current_phase: Object.freeze(['Current Phase']),
-    current_phase_name: Object.freeze(['Current Phase Name']),
-    current_plan: Object.freeze(['Current Plan']),
-    status: Object.freeze(['Status']),
-    // Scoped to `## Session` by the builder; see the presence check in
-    // `updateCore` for why the lookup here is deliberately unscoped.
-    stopped_at: Object.freeze(['Stopped At', 'Stopped at']),
-    paused_at: Object.freeze(['Paused At']),
-    last_activity: Object.freeze(['Last Activity', 'Last activity']),
-    last_activity_desc: Object.freeze(['Last Activity Description']),
-  } satisfies Record<string, readonly string[]>),
+  FRONTMATTER_BODY_SOURCE_KEY_ORDER.reduce((acc, key) => {
+    const row: StateFieldSchema = STATE_FIELD_SCHEMA[key];
+    acc[key] = Object.freeze([...(row.bodySource ?? [])]);
+    return acc;
+  }, Object.create(null) as Record<string, readonly string[]>),
 );
 
 /**