v2.21.0: AC Verification & Deferral Constraints

What's New

Implements 8 improvements (P1-P8) to prevent agents from claiming completion while acceptance criteria remain unmet. Based on a post-incident analysis of PRO-166 where implementation agents claimed COMPLETE twice while ~40-60% of AC remained unfulfilled.

Highlights

• AC Verification Step (3.4.2) — Orchestrator runs grep/glob verification commands against each AC after implementation reports COMPLETE
• Deferred Item Classification — New Classification column (AC-DEFERRED, DISCOVERED, OUT-OF-SCOPE) with user approval gate for AC deferrals
• Verification Commands in Code Review — Step 0 now requires running actual verification commands, not just reading code
• Schema Quality Standards — Blocks permissive z.record(z.unknown()), z.string() where enums exist
• Data Flow Tracing — Traces API parameters from boundary to consumer to catch silent data loss
• Component Rewrite Guidance — Destructive before constructive, verify each independently

Impact

All improvements work identically in both full context (1M) and budget (<500K) modes. 19 files changed across commands, agents, and skills.

Full changelog: CHANGELOG.md