feat(signals): delegate isTestFile to test-evidence isTestPath

[jaso0n0818]

Summary

Delegates isTestFile in local-branch.ts to isTestPath from test-evidence.ts so local scoring, slop, and contributor evidence share one test-path matcher (#561 / #1046 follow-up, extends #947).

Behavior:

• Removes the duplicated regex block in isTestFile
• Keeps e2e/integration/playwright/cypress/snapshot paths recognized consistently across surfaces

Test plan

• git diff --check
• npm run typecheck
• npm test -- test/unit/local-branch-file-classifiers.test.ts
• predicted gate: success (no duplicate blockers with open feat(signals): classify automation and CI toolchain config in path-matchers #1261/feat(signals): recognize e2e, integration, and snapshot test paths #1262)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.42%. Comparing base (fb935f4) to head (1778b95).
⚠️ Report is 1 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1306      +/-   ##
==========================================
- Coverage   95.42%   95.42%   -0.01%     
==========================================
  Files         193      193              
  Lines       21020    21019       -1     
  Branches     7614     7613       -1     
==========================================
- Hits        20058    20057       -1     
  Misses        383      383              
  Partials      579      579              

Files with missing lines	Coverage Δ
src/signals/local-branch.ts	97.19% <100.00%> (-0.01%)	⬇️

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[superagent-security]

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

[superagent-security]

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

[JSONbored]

Screen: ✅ low-risk signal hygiene. Verdict: MERGE-on-merit · hands-off, owner executes. Verified byte-identical bodies → behavior-preserving DRY consolidation, kills a drift hazard. Green.