Triage bot and PR-based claims (#2397)

* Claim bot: a PR referencing an issue claims it

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TPWBBSRPfPYWgrrhbznewR

* Triage bot: label new issues and PRs, /triage, backfill

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TPWBBSRPfPYWgrrhbznewR

* Docs: a draft PR is the claim; labels and triage

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TPWBBSRPfPYWgrrhbznewR

* Triage bot: start a runner only for events it acts on

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TPWBBSRPfPYWgrrhbznewR

---------

Co-authored-by: jyviko <2501648+jyviko@users.noreply.github.com>
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

.github/workflows/ci.yml

@@ -211,8 +211,8 @@ jobs:
         run: cargo xtask web-offline-test
       - name: Affected-package selection self-test
         run: python3 -I scripts/ci/test_affected.py
-      - name: Claim bot tests
-        run: node --test scripts/claim/*.test.js
+      - name: Claim and triage bot tests
+        run: node --test scripts/claim/*.test.js scripts/triage/*.test.js
 
   clippy:
     name: Native Linux Clippy