test(engine): merge predicted-gate-engine-branch-coverage.test.ts into predicted-gate-engine.test.ts

[JSONbored]

Closes #8575.

Summary

predicted-gate-engine-coverage.test.ts (1432 lines) and predicted-gate-engine-branch-coverage.test.ts (708 lines) were two disconnected #2283 bolt-ons against the same gate-advisory/predicted-gate-engine module family — both cite #2283 in their top-level describe. Merged into one file (predicted-gate-engine.test.ts) as two describe blocks, keeping every case verbatim — a pure relocation, no case retitled or dropped.

Given the density of these files (each it() block often exercises many branch arms across dozens of assertions), I did not attempt to dedupe individual assertions inside the mega-tests — too high a risk of silently dropping real coverage for a large mechanical merge. The consolidation win here is file organization: one home for the module family instead of two disconnected bolt-ons.

One identifier collision: both files declared a top-level REPO const with different shapes (the larger file's is a hand-written literal object; the smaller file's is repo("acme/widgets") from its own factory helper). Renamed the smaller file's to BRANCH_REPO throughout — everything else (repo()/pr() factory functions, all other imports) had zero collisions.

Test plan

• npx vitest run test/unit/predicted-gate-engine.test.ts — 33/33 pass
• npm run typecheck — clean
• Coverage regression check, before (both original files) vs after (merged): identical across every module the file exercises —
  • gate-advisory.ts: 219/225 branches (97.33%), 154/154 lines (100%)
  • predicted-gate-engine.ts: 332/339 branches (97.93%), 282/283 lines (99.64%)
  • cla-check.ts: 27/27 branches (100%), 13/13 lines (100%)
  • pre-merge-checks.ts: 33/34 branches (97.05%), 22/22 lines (100%)
  • change-guardrail.ts: 34/36 branches (94.44%), 45/45 lines (100%)
  • duplicate-winner.ts: 21/22 branches (95.45%), 19/19 lines (100%)

[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 91.99%. Comparing base (346c183) to head (59d3a9c).
⚠️ Report is 7 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #8584      +/-   ##
==========================================
- Coverage   92.54%   91.99%   -0.56%     
==========================================
  Files         796      796              
  Lines       79845    79845              
  Branches    24134    24134              
==========================================
- Hits        73896    73452     -444     
- Misses       4802     5309     +507     
+ Partials     1147     1084      -63     

Flag	Coverage Δ
backend	92.95% <ø> (-0.78%)	⬇️

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see 3 files with indirect coverage changes