enhance(spec-phase): edge-probe precision probe should name tie-breaking / rounding-mode (#1108)

* feat(spec-phase): name tie-breaking/rounding mode in the edge-probe precision probe (#1102)

The precision edge probe fired on numeric-range requirements but its text never
named the most common rounding failure mode — tie-breaking / rounding mode
(half-up vs half-to-even, ceil/floor/truncate). In an A/B experiment the weak
tier (haiku) false-passed 50% of tie-class defects against the surfaced-
unresolved spec; naming the rule in the probe text drove honest abstention
83%→100% (false-pass 17%→0%, haiku 50%→0%) with no category regression
(precision still fires only on numeric-range).

Sharpen the single TAXONOMY probe string and update every rendering together so
the doc↔fixture↔machine contract (edge-probe-docs-fixtures.test.cjs) stays green:
src/edge-probe.cts, the edge-probe.md taxonomy table + 2 worked examples, the
01-round-half-even and 04-money-rounding fixtures, and the resolve-edge-coverage
how-to. Prose-only — no consumer keys on the probe text; SHAPE_CUES firing
unchanged; fully backward compatible.

* chore(changeset): Changed fragment for edge-probe precision probe text (#1108)

.changeset/graceful-zebras-munch.md

@@ -0,0 +1,5 @@
+---
+type: Changed
+pr: 1108
+---
+Edge-probe `precision` probe text now names tie-breaking / rounding-mode (half-up vs half-to-even, ceil/floor/truncate), so a surfaced precision edge cues the most common rounding failure mode. Prose-only; firing rule and the 8-category core unchanged.

docs/how-to/resolve-edge-coverage-findings.md

@@ -12,7 +12,7 @@ For the category taxonomy and the reasoning behind front-of-pipeline edge analys
 
 Each finding is one **applicable** edge for one requirement — a boundary the probe's relevance filter decided is in scope for that requirement's shape, and that you have not yet addressed. A finding is phrased as a probe question, for example:
 
-> **R3 · precision** — Where can precision loss or overflow occur, and what is the contract?
+> **R3 · precision** — Where can precision loss, overflow, or rounding/tie-breaking occur — and what is the exact contract (e.g. half-up vs half-to-even, ceil/floor/truncate)?
 
 You must resolve each finding into exactly one of four states. Claude presents them as a numbered choice (or an `AskUserQuestion` menu).
 

gsd-core/references/edge-probe-fixtures/01-round-half-even/expected-coverage.json

@@ -1,7 +1,7 @@
 {
   "items": [
     { "requirement_id": "R1", "category": "boundary", "status": "unresolved", "verification": null, "resolution": null, "reason": null, "probe": "What happens exactly at each min/max/threshold — and one step either side?" },
-    { "requirement_id": "R1", "category": "precision", "status": "unresolved", "verification": null, "resolution": null, "reason": null, "probe": "Where can precision loss or overflow occur, and what is the contract?" }
+    { "requirement_id": "R1", "category": "precision", "status": "unresolved", "verification": null, "resolution": null, "reason": null, "probe": "Where can precision loss, overflow, or rounding/tie-breaking occur — and what is the exact contract (e.g. half-up vs half-to-even, ceil/floor/truncate)?" }
   ],
   "coverage": { "applicable": 2, "resolved": 0, "unresolved": 2, "byVerification": { "explicit": 0, "backstop": 0 } }
 }

gsd-core/references/edge-probe-fixtures/04-money-rounding/expected-coverage.json

@@ -1,7 +1,7 @@
 {
   "items": [
     { "requirement_id": "R1", "category": "boundary", "status": "unresolved", "verification": null, "resolution": null, "reason": null, "probe": "What happens exactly at each min/max/threshold — and one step either side?" },
-    { "requirement_id": "R1", "category": "precision", "status": "unresolved", "verification": null, "resolution": null, "reason": null, "probe": "Where can precision loss or overflow occur, and what is the contract?" }
+    { "requirement_id": "R1", "category": "precision", "status": "unresolved", "verification": null, "resolution": null, "reason": null, "probe": "Where can precision loss, overflow, or rounding/tie-breaking occur — and what is the exact contract (e.g. half-up vs half-to-even, ceil/floor/truncate)?" }
   ],
   "coverage": { "applicable": 2, "resolved": 0, "unresolved": 2, "byVerification": { "explicit": 0, "backstop": 0 } }
 }

gsd-core/references/edge-probe.md

@@ -62,7 +62,7 @@ truncation). Growth happens via optional domain packs, not by bloating the core.
 | empty | Empty / degenerate | collection, text | What is the result for empty, single-element, or null input? |
 | encoding | Encoding / representation | text | Whose definition of length/equality applies — bytes, code points, grapheme clusters, or normalized form? |
 | ordering | Ordering / stability | collection | When elements compare equal, is output order specified and stable? |
-| precision | Precision / overflow | numeric-range | Where can precision loss or overflow occur, and what is the contract? |
+| precision | Precision / overflow | numeric-range | Where can precision loss, overflow, or rounding/tie-breaking occur — and what is the exact contract (e.g. half-up vs half-to-even, ceil/floor/truncate)? |
 | idempotency | Idempotency / repetition | stateful | What happens if this runs twice on the same input? |
 | concurrency | Concurrency / effect ordering | stateful, io | If interrupted or run in parallel, what is guaranteed? |
 
@@ -170,7 +170,7 @@ rule, the requirement classifies as `numeric-range`, which raises `boundary` and
 {
   "items": [
     { "requirement_id": "R1", "category": "boundary", "status": "unresolved", "verification": null, "resolution": null, "reason": null, "probe": "What happens exactly at each min/max/threshold — and one step either side?" },
-    { "requirement_id": "R1", "category": "precision", "status": "unresolved", "verification": null, "resolution": null, "reason": null, "probe": "Where can precision loss or overflow occur, and what is the contract?" }
+    { "requirement_id": "R1", "category": "precision", "status": "unresolved", "verification": null, "resolution": null, "reason": null, "probe": "Where can precision loss, overflow, or rounding/tie-breaking occur — and what is the exact contract (e.g. half-up vs half-to-even, ceil/floor/truncate)?" }
   ],
   "coverage": { "applicable": 2, "resolved": 0, "unresolved": 2, "byVerification": { "explicit": 0, "backstop": 0 } }
 }
@@ -209,7 +209,7 @@ classifies as `numeric-range`, which raises `boundary` and `precision`:
 {
   "items": [
     { "requirement_id": "R1", "category": "boundary", "status": "unresolved", "verification": null, "resolution": null, "reason": null, "probe": "What happens exactly at each min/max/threshold — and one step either side?" },
-    { "requirement_id": "R1", "category": "precision", "status": "unresolved", "verification": null, "resolution": null, "reason": null, "probe": "Where can precision loss or overflow occur, and what is the contract?" }
+    { "requirement_id": "R1", "category": "precision", "status": "unresolved", "verification": null, "resolution": null, "reason": null, "probe": "Where can precision loss, overflow, or rounding/tie-breaking occur — and what is the exact contract (e.g. half-up vs half-to-even, ceil/floor/truncate)?" }
   ],
   "coverage": { "applicable": 2, "resolved": 0, "unresolved": 2, "byVerification": { "explicit": 0, "backstop": 0 } }
 }

src/edge-probe.cts

@@ -88,7 +88,7 @@ export const TAXONOMY: TaxonomyEntry[] = [
   { id: 'empty', name: 'Empty / degenerate', shapes: ['collection', 'text'], probe: 'What is the result for empty, single-element, or null input?' },
   { id: 'encoding', name: 'Encoding / representation', shapes: ['text'], probe: 'Whose definition of length/equality applies — bytes, code points, grapheme clusters, or normalized form?' },
   { id: 'ordering', name: 'Ordering / stability', shapes: ['collection'], probe: 'When elements compare equal, is output order specified and stable?' },
-  { id: 'precision', name: 'Precision / overflow', shapes: ['numeric-range'], probe: 'Where can precision loss or overflow occur, and what is the contract?' },
+  { id: 'precision', name: 'Precision / overflow', shapes: ['numeric-range'], probe: 'Where can precision loss, overflow, or rounding/tie-breaking occur — and what is the exact contract (e.g. half-up vs half-to-even, ceil/floor/truncate)?' },
   { id: 'idempotency', name: 'Idempotency / repetition', shapes: ['stateful'], probe: 'What happens if this runs twice on the same input?' },
   { id: 'concurrency', name: 'Concurrency / effect ordering', shapes: ['stateful', 'io'], probe: 'If interrupted or run in parallel, what is guaranteed?' },
 ];