feat(quality-gate): implement pitfall-catalog validation for dead code (Story 2.4)
Create pitfalls-catalog.json with 6 false-positive pattern categories for
find_dead_code. Implement validate-dead-code.mjs classification engine
(SUSPECT/FALSE_POS/GHOST) with 10s timeout, input validation, null
guards, file size/candidate caps, and unique test filenames.
Integrate as Step 5c in bmad-dev-story, bmad-quick-dev workflows, and
expand code-review Acceptance Auditors in bmad-code-review and
gds-code-review.
Code review patches applied: status conditional, TimeoutError class,
fail() scoped timeout token, JSON parse error context, single regex
compilation, null/type guards, MSW pattern fix, Ignored section for
FALSE_POS/GHOST in SKILL.md.
Tests: 12/12 validate-dead-code + 10/10 qa-memtrace passing.
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