feat(github-app): add PR panel rerun checkbox

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Summary

• Add a maintainer-facing rerun checkbox to the sticky Gittensory PR panel.
• Handle checked task-list edits on the bot-authored panel by rerunning the normal PR public-surface pipeline and resetting the checkbox in place.

What changed

• Added a stable hidden rerun marker below Contributor next steps.
• Added an issue_comment.edited handler that only accepts checked rerun tasks on Gittensory's own sticky panel.
• Audits successful and skipped rerun attempts without creating duplicate comments.
• Added unit coverage for rerun, ignored edits, skipped reruns, and closed-PR defensive paths.

Why

Maintainers need a low-friction way to refresh Gittensory's PR review data after other PRs merge or repo context changes, without posting a new bot comment.

Validation

• npx vitest run test/unit/signals-coverage.test.ts test/unit/queue.test.ts
• npm run typecheck
• npm run test:coverage
• npm run test:ci

[ghost]

Note

Gittensory Gate skipped

PR closed before full evaluation. No late first comment was created.

Signal	Result	Evidence	Action
Gate result	⚠️ Skipped	#431 is no longer open.	No action.

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Checked by Gittensory, a quiet PR intelligence layer for OSS maintainers.