rosetta[yacc]: cross-language consistency — 9 red / 3 amber metrics, 3 ledgered shapes

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Part of #2560 — per-language tracking for the keyword-rosetta control corpus (built for #1096). Planted intent is identical in every language, so every deviation below is measured bias vs. the 46-language median, validated in the corpus's deviation ledger. 🔴 = beyond ±50% of the cross-language median, 🟡 = ±25–50%.

Triage order (per the epic): structure detection first, then signal/keyword rules, then risk-score consequences — §3's numbers are downstream of §1–§2 and re-baseline as those fix. Cross-cutting engine issues (e.g. #2535/#2546) fix many languages at once; this issue tracks this language's residual after each cross-cutting fix lands, and closes when the language sits inside the ±25% band on every comparable metric (or every remaining deviation is ledgered as intended morphology).

1. Structure detection (fix first)

• 🔴 args: 2 vs median 13 (-85%)
• 🔴 dependency_links: 0 vs median 3 (-100%)

2. Signal / keyword deviations

• 🔴 state_mutation: 2 vs median 6 (-67%)
• 🔴 test: 0 vs median 2 (-100%)
• 🟡 branch: 3 vs median 5 (-40%)
• 🟡 keyword_hits: 153 vs median 247.5 (-38%)

3. Risk-exposure consequences (downstream)

• 🔴 risk_api_exposure: 0 vs median 5.31104 (-100%)
• 🔴 risk_cognitive_load: 4 vs median 15.1444 (-74%)
• 🔴 risk_documentation: 27.1891 vs median 57.1208 (-52%)
• 🔴 risk_spec_match: 46.6667 vs median 96 (-51%)
• 🔴 risk_tech_debt: 80 vs median 39.9576 (+100%)
• 🟡 risk_verification: 1.30806 vs median 2.3628 (-45%)

Ledgered shapes touching yacc

defect	type	issue	evidence	summary
census-requires-git-tracked	engine-semantic	—	—	GalaxyScope's census enumerates git-tracked files only; an untracked folder scans as '0 files mapped' with no per-file warning
batch5-tier2-morphology-shapes	keyword-overlap	—	—	Collective entry for Tier-2 finditer/report-confirmed shapes, detailed per-manifest: css at-rules triple-count (func+branch, @supports also safety; args tracks @import u…
no-dependency-capture-languages	upstream-question	—	(notes)	m4 and scheme have _dependency_capture = None: include()/(import ...) count the import signal but can never produce a DAG edge, so popularity stays 0 and orphans never c…

Reproduce / evidence

• Corpus folder: data/yacc/ — expected_signals.json carries the shape-by-shape accounting
• Gate: GALAXYSCOPE_BIN=<venv>/bin/galaxyscope python tools/verify_language.py yacc in the corpus repo
• Full context: findings_by_language.md#yacc · bias_report.md · bias chart