fix(#2440): per-counter progress ratchet — total_plans always takes derived value (#2468)

* fix(#2440): per-counter progress ratchet — total_plans always takes derived value

Two sites fixed (targeted — existing body-only write tests preserved):

Site A — read path: shouldPreserveExistingProgress (state-document.cts:167)
removed total_plans from the all-or-nothing ratchet check. It now joins
total_phases as an always-derived counter. Only completed_phases and
completed_plans keep ratchet behaviour (they are monotonic). This fixes
gsd-tools query state.json reporting stale total_plans when a curated
completed_plans triggers the ratchet.

Site B — write path: applyStatePreservation (state-transition.cts:162)
gained a deriveProgressKeys opt-in flag. When true (passed by
cmdStatePlannedPhase only), total_plans and total_phases take the
derived (post-sync) value instead of the wholesale curated restore.
When false (the default — state.update, state.patch), the existing
#3242 wholesale protection stays fully in force. This fixes the
state planned-phase verb writing a stale total_plans.

The opt-in approach preserves all 8 existing #3242/#1264/#500 body-only
write tests that assert wholesale progress preservation during non-
progress updates.

Tests:
- tests/state.test.cjs: 4 unit tests for shouldPreserveExistingProgress
  (total_plans upward/downward/equality + completed_plans ratchet active).
- tests/state-transition.test.cjs: 2 #2440 regression tests for
  deriveProgressKeys=true (total_plans takes derived; boundary at equality).
  The existing !resync wholesale-restore test stays unchanged (default
  behavior preserved).

References: #2440; #1446 (total_phases read-path fix — same principle);
#3242 Bug A (body-only preservation — protection preserved via the opt-in
gate); ADR-1769 (applyStatePreservation table-driven preservation).

* chore(#2440): backfill pr:2468 in .changeset/mellow-eagles-chatter.md

src/state.cts

@@ -63,6 +63,8 @@ interface StateLockClock {
 
 interface ReadModifyWriteOptions {
   resync?: boolean;
+  /** #2440: when true, total_plans/total_phases take derived values even under !resync. */
+  deriveProgressKeys?: boolean;
 }
 
 interface StateRecordMetricOptions {
@@ -2117,6 +2119,7 @@ function readModifyWriteStateMd(statePath: string, transformFn: (content: string
     const postFm = extractFrontmatter(synced) as Record<string, unknown>;
     const preservation = applyStatePreservation({
       preFm, postFm, preFmSnapshot, resync,
+      deriveProgressKeys: options?.deriveProgressKeys === true,
       preBodyStatus, postBodyStatus,
       preBodyStoppedAt, postBodyStoppedAt,
       preBodyPhaseSource, postBodyPhaseSource,
@@ -2477,7 +2480,7 @@ function cmdStatePlannedPhase(cwd: string, phaseNumber: string | number, planCou
     const result = transitionCore(content, intent, deps);
     updated = result.updated;
     return result.content;
-  }, cwd, { resync: false });
+  }, cwd, { resync: false, deriveProgressKeys: true });
 
   output({ updated, phase: phaseNumber, plan_count: planCount }, raw, updated.length > 0 ? 'true' : 'false');
 }