fix(signals): drop the stale v8-ignore on buildCollisionReport's pairwise loop

[JSONbored]

Summary

• Follow-up to fix(signals): require a real shared file before path-driven PR collisions cluster #2696 (merged before I could push this): codecov/patch flagged the path-overlap guard at 66.66% because the whole pairwise loop in buildCollisionReport was wrapped in a /* v8 ignore start/stop */ comment that predates real per-branch test coverage for it.
• Confirmed via the full unsharded suite that removing the ignore reveals zero new gaps — engine.ts stays at 99.25% stmts / 97.94% branch, with the exact same 3 pre-existing, unrelated uncovered lines (just shifted by the 2 deleted comment lines). The loop is fully exercised by the existing + fix(signals): require a real shared file before path-driven PR collisions cluster #2696's new collision tests; the ignore was simply stale.
• No behavior change — comment-only deletion.

Scope

• Conventional Commit title.
• Focused, single change (2 lines removed).
• Follows CONTRIBUTING.md.
• No fresh issue needed — direct follow-up to fix(signals): require a real shared file before path-driven PR collisions cluster #2696's codecov/patch finding.

Validation

• npm run typecheck
• npm run test:coverage locally, unsharded — full suite green, engine.ts 99.25%/97.94% branch, no new uncovered lines
• Targeted re-run of test/unit/signals-v2.test.ts, signals-coverage.test.ts, signals.test.ts — all pass

Safety

• No secrets/private data exposed.
• N/A — no auth/UI/API/docs surface touched.

Notes

• Comment-only change; this is purely fixing coverage reporting accuracy for the diff, not adding new tested behavior.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.11%. Comparing base (dc90617) to head (e3a7340).
⚠️ Report is 14 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2714      +/-   ##
==========================================
- Coverage   96.13%   96.11%   -0.02%     
==========================================
  Files         241      241              
  Lines       27033    27057      +24     
  Branches     9822     9834      +12     
==========================================
+ Hits        25988    26006      +18     
  Misses        433      433              
- Partials      612      618       +6     

Files with missing lines	Coverage Δ
src/signals/engine.ts	97.35% <ø> (-0.32%)	⬇️

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