fix(review): trust a linked issue closed by this PR's own merge for label propagation

[JSONbored]

Summary

• Merging a PR with Closes #N auto-closes issue #N as an immediate side effect of the merge. resolveIssueLabelsForPropagation (src/review/linked-issue-label-propagation-fetch.ts) only trusted an open linked issue, so the next time the type-label decision ran for that PR (a near-simultaneous webhook, or the periodic sweep), it found the issue closed, propagation returned no labels, and the code fell back to a blunt title-regex guess — actively removing the correct gittensor:feature/gittensor:priority labels it had just applied seconds earlier and replacing them with gittensor:bug.
• Extends the trust condition (isLinkedIssueTrustworthy) to also accept a closed issue when it was closed at or after this PR's own merge — i.e. closed as a byproduct of this exact PR's "Closes #N" merge, GitHub's standard auto-close. An issue closed before this PR merged still doesn't count, preserving the original anti-gaming intent (a PR can't borrow a label from some unrelated, already-resolved issue).
• Adds closedAt to the linked-issue facts fetch (src/github/backfill.ts) — same REST payload, no new API call — and threads prMergedAt from the PR's own mergedAt through the propagation fetch call site (src/queue/processors.ts).

Closes #4528

Scope

• The PR title follows type(scope): short summary Conventional Commit format.
• This PR is focused and does not mix unrelated backend, UI, MCP, docs, dependency, and deploy changes.
• This follows CONTRIBUTING.md and does not reintroduce GitHub Pages, VitePress, site/, or CNAME.
• I linked a currently open issue this PR resolves.

Validation

• git diff --check
• npm run typecheck
• Targeted unit/integration coverage: test/unit/backfill.test.ts, test/unit/linked-issue-label-propagation-fetch.test.ts, test/unit/linked-issue-hard-rules.test.ts, test/unit/queue.test.ts — 1175/1175 passing, including a full webhook-simulation regression test reproducing the exact PR feat(miner-manage-ui): fold run-state into the manage-status panel #4494 incident.
• npm audit --audit-level=moderate — 0 vulnerabilities
• New/changed behavior has unit/integration tests for new branches (open issue / closed-by-this-merge / closed-before-this-merge / closed-with-no-closed_at fallback) and a named regression test for the bug.
• npm run actionlint, npm run test:workers, npm run build:mcp, npm run test:mcp-pack, npm run ui:openapi:check, npm run ui:lint, npm run ui:typecheck, npm run ui:build — not run locally; this diff is scoped entirely to src/github/backfill.ts, src/review/linked-issue-label-propagation-fetch.ts, and src/queue/processors.ts (no UI/MCP/OpenAPI/wrangler/workers surface touched), so CI's full test:ci gate covers these.
• npm run test:coverage (full unsharded) — kicked off locally but not confirmed complete before pushing; Codecov's codecov/patch check on this PR is the authoritative signal.

Safety

• No secrets, wallet details, hotkeys, coldkeys, user PATs, private keys, raw trust scores, private rankings, or private maintainer evidence are exposed.
• Public GitHub text stays sanitized, low-noise, and does not imply compensation guarantees or optimization tactics.
• No auth/cookie/CORS/GitHub App/Cloudflare/session changes.
• No API/OpenAPI/MCP surface changed.
• No UI changes.
• No public docs/changelog changes needed.

Notes

Root-caused via a live-audit-log investigation: 87 real label downgrades across gittensory + metagraphed in a 49-hour window, 79 still wrong on GitHub at time of filing, 39 with the gittensor:priority reward multiplier permanently lost. Backfill of the currently-mislabeled PRs is a separate follow-up, tracked outside this PR.

[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 94.04%. Comparing base (23693c3) to head (4a390b0).
⚠️ Report is 1 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4534   +/-   ##
=======================================
  Coverage   94.04%   94.04%           
=======================================
  Files         422      422           
  Lines       37574    37579    +5     
  Branches    13724    13729    +5     
=======================================
+ Hits        35335    35340    +5     
  Misses       1583     1583           
  Partials      656      656           

Files with missing lines	Coverage Δ
src/github/backfill.ts	97.07% <100.00%> (+<0.01%)	⬆️
src/queue/processors.ts	95.39% <100.00%> (+<0.01%)	⬆️
src/review/linked-issue-label-propagation-fetch.ts	100.00% <100.00%> (ø)

🚀 New features to boost your workflow:

• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.