fix(search): prevent stale dialog request state

[llbbl]

Closes #74

Summary

• Add active AbortController ownership guards so only the current request can update loading, errors, and results.
• Cancel pending debounce and in-flight search work immediately when the query changes or the dialog closes, then reset dialog state before reopen.
• Add overlap and close/reopen regression coverage for stale-response handling and successful active-request results.

Validation

• pnpm format
• pnpm lint
• pnpm exec tsc --noEmit
• pnpm test --run (162 tests)
• pnpm test:coverage --run (overall line coverage 94.48%; Search.tsx line coverage 95.12%)
• pnpm db:init:local
• pnpm index:local (3/3 documents)
• env TURSO_DB_URL=file:local.db TURSO_AUTH_TOKEN=local pnpm build

[codecov]

Codecov Report

❌ Patch coverage is 91.89189% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.33%. Comparing base (9797866) to head (c6c18f4).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/components/Search.tsx	91.89%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #90      +/-   ##
==========================================
+ Coverage   83.62%   89.33%   +5.70%     
==========================================
  Files          12       12              
  Lines         287      300      +13     
  Branches       72       71       -1     
==========================================
+ Hits          240      268      +28     
+ Misses         28       16      -12     
+ Partials       19       16       -3     

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