fix(review): preserve fallback classification for invalid/absent inline finding categories

[JSONbored]

Motivation

• A recent parser change forced every model-emitted inline finding to carry a concrete category (defaulting to maintainability), which prevented deterministic path/body fallback from classifying security-like findings as security when the model omitted or mis-emitted the field.

Description

• Stop injecting a parser default category: parseInlineFindingCategory now returns FindingCategory | undefined and returns undefined when the model value is absent or invalid so downstream fallback can run. (src/review/inline-finding-category-parse.ts)
• Only attach category into parsed inline findings when the model value is a valid enum; use conditional spreading to omit the field when absent. (src/services/ai-review.ts)
• Update unit tests to reflect the new behavior and add a regression test that verifies a security-like finding with an invalid model category falls back to security. (test/unit/inline-finding-category-parse.test.ts, test/unit/ai-review.test.ts)
• Files changed: src/review/inline-finding-category-parse.ts, src/services/ai-review.ts, test/unit/inline-finding-category-parse.test.ts, test/unit/ai-review.test.ts.

Testing

• Typecheck: ran npm run typecheck and it succeeded.
• Unit tests: ran npx vitest run test/unit/inline-finding-category-parse.test.ts test/unit/ai-review.test.ts test/unit/inline-comments-select.test.ts --pool=forks and all tests passed (suite completed successfully).
• Security audit: ran npm audit --audit-level=moderate but the registry audit endpoint returned 403 Forbidden in this environment, so the audit could not be completed here.

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Codex Task

[superagent-security]

Superagent didn't find any vulnerabilities or security issues in this PR.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.95%. Comparing base (c823f9c) to head (2a178d3).
⚠️ Report is 12 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4385   +/-   ##
=======================================
  Coverage   93.95%   93.95%           
=======================================
  Files         400      400           
  Lines       36817    36817           
  Branches    13451    13452    +1     
=======================================
  Hits        34592    34592           
  Misses       1569     1569           
  Partials      656      656           

Files with missing lines	Coverage Δ
src/review/inline-finding-category-parse.ts	100.00% <100.00%> (ø)
src/services/ai-review.ts	96.59% <100.00%> (+<0.01%)	⬆️

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