classifier-fingerprint: looks_like_ai drift from PR #3537 not acknowledged

[Sinity]

Summary

`devtools lab policy classifier-fingerprints` reports an undeclared fingerprint drift for `polylogue/sources/parsers/claude/ai_parser.py:looks_like_ai`, discovered while verifying an unrelated PR (polylogue-3uw, capture-completeness coverage) whose pre-push quick-verify gate runs this check repo-wide regardless of the files that PR touches.

Evidence

• `devtools lab policy classifier-fingerprints` fails with: "classification functions with undeclared fingerprint drift: 1 ... polylogue/sources/parsers/claude/ai_parser.py:looks_like_ai".
• `git log -3 --oneline -- polylogue/sources/parsers/claude/ai_parser.py` shows the most recent change is d921ef0 ("feat(sources): add per-file acquisition logging and tighten claude-ai detection (feat(sources): add per-file acquisition logging and tighten claude-ai detection #3537)"), whose own PR body states it deliberately "tightens the loosest remaining 'guess and proceed' detector (`claude.looks_like_ai`) to require positive structural evidence" — a real, intentional decision-boundary change, just not run through/recorded in `docs/plans/classifier-fingerprints.json` at push time.
• The classifier-fingerprint gate itself (`devtools lab policy classifier-fingerprints`) was added by 1a2ea50 ("feat(devtools): gate parser/classifier decision-boundary drift (feat(devtools): gate parser/classifier decision-boundary drift #3532)"), which landed before feat(sources): add per-file acquisition logging and tighten claude-ai detection #3537 per `git log` ordering, so feat(sources): add per-file acquisition logging and tighten claude-ai detection #3537 should have been caught by its own pre-push gate and was not (or the ack step was skipped/missed).

Ask

Determine whether #3537's `looks_like_ai` tightening needs an `INDEX_SCHEMA_VERSION` bump with a declared `SEMANTIC_REPARSE` delta (already-indexed Claude-AI-adjacent rows may be classified differently under the tightened rule), or whether it's safe as a retroactive `acknowledged_safe` entry (matching the existing `polylogue-zqph` precedent for the same class of gap from PR #3428). Until resolved, every push in the repo fails `devtools verify --quick``'s `lab policy classifier-fingerprints` step, since it is repo-wide and un-scoped to the changed files of the pushing branch.

Discovered while working polylogue-3uw; unrelated to that bead's scope.