perf(projects): coordinate filtered reads and purge

[beruro]

Summary

• deduplicate concurrent filtered Work Item view reads without retaining query-specific results in the project read cache
• share concurrent expired-item purge calls and throttle successful follow-up purges per project for five minutes
• invalidate project cache only when a purge actually removes rows
• bound purge coordination state to 50 project keys and release failed requests for retry

Validation

• focused Vitest suite: 5 passed
• pnpm exec tsc --noEmit --pretty false
• Prettier and ESLint on all changed files
• git diff --check

Performance guard

Pass. The change adds no timer or polling loop. Work is caller-demand driven, concurrent requests are single-flight, filtered results are not retained, purge cadence is monotonic by successful completion time, and retained coordinator state has an explicit 50-project cap.

Architecture audit

Covered compilation, request-state ownership, cache invalidation fencing, semantic defaults, and lifecycle/error parity. Wire payloads and resolver behavior are unchanged.