Bound snapshot cache invalidation (codex)

[numnx]

🧩 Task: Bound snapshot cache invalidation

Automated task PR opened by Code UX for T03.

📋 Summary

Sprint: Sprint 142 · QS: Code Quality & Performance Audit · Task: T03

Audit and improve Code UX quality and performance by tightening existing hot-path contracts across live snapshots, execution projection, provider telemetry, dashboard render derivation, repository boundaries, MCP validation, guardrails, and documentation.

📝 Full Task Prompt

## Objective
Improve dashboard snapshot cache invalidation by tracking cache keys per project so hot realtime invalidations do not scan every cached project/query key.

## Scope
- Edit `src/app/lifecycle/dashboard-snapshot-cache.ts`
- Edit `src/app/lifecycle/dashboard-snapshot-cache-policy.ts` only if a key parsing helper is needed
- Edit `tests/backend/app/lifecycle/dashboard-snapshot-cache.test.ts`
- Update `docs/architecture/code-quality-performance-contracts.md` cache policy notes if the invalidation contract changes

## Implementation Requirements
1. Add private project-to-cache-key indexes for full execution snapshots, lean execution snapshots, and project stats snapshots inside `DashboardSnapshotCache`.
2. Register keys when setting cache entries and remove them when invalidating a project, invalidating stats, or clearing all caches.
3. Keep `DashboardSnapshotCachePolicy.getProjectExecutionSnapshotCacheKey`, `getProjectStatsCacheKey`, and existing cache key string formats backward compatible unless tests prove a safer helper is needed.
4. Add tests that seed multiple project cache entries, invalidate one project, and assert only that project’s full/lean execution and stats entries are removed while unrelated project entries remain cached.

## Constraints
- Do not change API response shapes for `/api/live`, `/api/execution`, or project stats.
- Preserve lean snapshot source identity behavior so feed-less snapshots do not survive a full snapshot rebuild.
- Keep cache TTL values centralized in `DashboardSnapshotCachePolicy`.
- Avoid broad repository or dashboard-server edits in this task.

## Verification
- Run `pnpm exec vitest run tests/backend/app/lifecycle/dashboard-snapshot-cache.test.ts`.
- Run `pnpm run lint`.
- Success means invalidating one project no longer requires scanning unrelated project cache keys and existing snapshot cache behavior remains compatible.

✅ QA Review

⏳ QA review runs after this PR is opened. Check the task card in the dashboard for the outcome once it lands.

🤖 Model & Provider

Provider	Codex CLI
Model	gpt-5.5

⏱️ Timing

Started	2026-07-06 18:05:03 UTC
Finished	2026-07-06 18:07:58 UTC
Duration	2m 54s

📊 Token Usage

Metric	Value
Input tokens	65,978
Cached input tokens	413,824
Output tokens	5,057
Total tokens	484,859
Invocations	1
Tool calls	22
Active time	2m 15s

Included usage estimate (subscription/local login): $0.69

🌿 Branch Info

Base: feature/CODUX-142-qs-code-quality-performance-audit-6
Head: task/feature-codux-142-qs-code-quality-performance-au-t03-codex-mr9j5n3h

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🤖 Generated by Code UX