Optimize project edit hot path

[melonamin]

Summary

• debounce project persistence and flush pending writes on lifecycle boundaries
• synchronize only changed worker files while preserving exact snapshot ordering
• prevent stale analysis and cache restores from replacing explicit results
• preserve backend file references across unchanged polling responses
• add regression coverage for persistence, worker synchronization, and async analysis races

Validation

• mise exec yarn@1.22.19 -- just check
• codex review — no actionable defects

[codecov]

Codecov Report

❌ Patch coverage is 78.78151% with 101 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
app/src/lib/analysis-worker.ts	77.84%	39 Missing ⚠️
app/src/hooks/useAnalysis.ts	82.50%	34 Missing and 1 partial ⚠️
app/src/lib/backend-adapter.ts	0.00%	18 Missing ⚠️
app/src/lib/project-store.tsx	87.09%	4 Missing ⚠️
app/src/workers/analysis.worker.ts	0.00%	3 Missing ⚠️
app/src/components/EditorArea.tsx	0.00%	2 Missing ⚠️

📢 Thoughts on this report? Let us know!