feat(react): add usage diff and benchmark coverage

[async3619]

Summary

• Add Git-based React usage diff analysis with ASCII/JSON output support.
• Add benchmark coverage for React diff, React file analysis, import graph building, and deps diff paths.
• Expand tests and README coverage for the new diff mode and git buffer handling.

Related Issue

N/A

Validation

• pnpm run check
• Commits follow Conventional Commits
• Branch name follows codex/issue-<number>-<slug>
• This PR will be Squash Merged into dev

Notes

• Verified with pnpm run typecheck, React/deps e2e tests, and targeted Vitest bench runs.

[codecov]

Codecov Report

❌ Patch coverage is 49.04110% with 186 lines in your changes missing coverage. Please review.
✅ Project coverage is 66.08%. Comparing base (2e97e90) to head (800f76d).
⚠️ Report is 5 commits behind head on dev.

Files with missing lines	Patch %	Lines
src/analyzers/react/diff.ts	50.73%	82 Missing and 52 partials ⚠️
src/output/ascii/react.ts	44.61%	24 Missing and 12 partials ⚠️
src/output/json/react.ts	55.00%	0 Missing and 9 partials ⚠️
src/commands/react.ts	0.00%	7 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##              dev     #107      +/-   ##
==========================================
- Coverage   68.79%   66.08%   -2.72%     
==========================================
  Files          38       39       +1     
  Lines        2221     2586     +365     
  Branches      714      857     +143     
==========================================
+ Hits         1528     1709     +181     
- Misses        408      520     +112     
- Partials      285      357      +72     

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[codspeed-hq]

Merging this PR will not alter performance

✅ 9 untouched benchmarks
🆕 9 new benchmarks

Performance Changes

	Benchmark	BASE	HEAD	Efficiency
🆕	component-only diff	N/A	26.6 ms	N/A
🆕	basic fixture	N/A	2.4 ms	N/A
🆕	full component and hook diff	N/A	25.8 ms	N/A
🆕	monorepo fixture	N/A	1.2 ms	N/A
🆕	styled entry with builtin tracking	N/A	2.1 ms	N/A
🆕	basic fixture without unused-import tracking	N/A	2.2 ms	N/A
🆕	manifest specifier change	N/A	10.4 ms	N/A
🆕	workspace source change	N/A	15.1 ms	N/A
🆕	AppShell symbol analysis	N/A	489.3 µs	N/A

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_{Comparing async3619/react-tree-diff (800f76d) with dev (2e97e90)¹}

Footnotes

1. No successful run was found on dev (97f2aae) during the generation of this report, so 2e97e90 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

[async3619]

🎉 This PR is included in version 1.2.0-dev.1 🎉

The release is available on:

• npm package (@dev dist-tag)
• GitHub release

Your semantic-release bot 📦🚀