plan(policy-quality): implementation plan for 4-track V7 audit
Produced by superpowers:writing-plans from the approved spec at
docs/superpowers/specs/2026-04-21-policy-quality-design.md.
Plan structure:
* Phase 0 (tasks 0.1-0.17): measurement substrate — TDD-detailed,
exact code + commands. Produces 6 new smoke tests + ~25 HEALTH_DIAG
fields across 4 tracks.
* Phase 1 (tasks 1.0-1.5): parallel investigation tracks — process
tasks (run instrumentation, record evidence, classify hypotheses).
No code to pre-write; output is 4 triage documents + a Phase-2
planning doc.
* Phase 2 (template only): convergence fix. Concrete tasks produced
by a Phase-2-specific plan AFTER Phase 1 triage — can't pre-write
the fixes without knowing which hypotheses confirm.
* Phase 3 (tasks 3.1-3.4): L40S validation gates, surrogate-noise,
branch decision (merge or iterate).
* Phase 4 (tasks 4.1-4.4): merge via --no-ff, tag, cleanup.
* Rollback procedure: git reset --hard policy-quality-baseline.
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