* feat(#836): no-LLM duplicate-issue detection + challenge + 1-day auto-close
Adds a deterministic (no-LLM) duplicate-issue governance lifecycle:
- scripts/issue-dedupe.cjs: pure, unit-tested module (tokenize, Sørensen–Dice
title similarity, scoreCandidates, renderChallengeComment, shouldClose) with
fail-safe destructive-action guards.
- duplicate-check.yml (issues:opened): scores new-issue title against open
issues, posts a challenge comment + applies the pending `possible-duplicate`
label on a clear match.
- duplicate-sweep.yml (daily cron): closes possible-duplicate issues whose
challenge comment is >24h old with no human reply and no 👎 veto; honors
exempt labels; re-checks the label immediately before close (TOCTOU guard);
strips the label on close to avoid reopen loops.
- remove-duplicate-label.yml (issue_comment:created): clears the label and
applies needs-maintainer-review when any human responds.
- bug_report.yml / docs_issue.yml: add the required "I searched existing
issues" preflight checkbox so all five forms force a pre-search attestation.
- docs/agents/triage-labels.md: document the label + lifecycle.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
* chore(#836): add changeset fragment for duplicate-issue detection
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>
