Claim bot: /claim and /unclaim on issues (#1584)

Comment /claim on an issue to be assigned and get the in progress label; /unclaim releases it. A daily sweep frees claims with no PR after 72 h or with a PR idle for 14 days.

.github/workflows/ci.yml

@@ -125,6 +125,8 @@ 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
 
   clippy:
     name: Native Linux Clippy

.github/workflows/claim.yml

@@ -0,0 +1,44 @@
+# `/claim` and `/unclaim` on issues (CONTRIBUTING.md, "Sending a change"), and a daily sweep that
+# frees claims nobody is working on. The logic is in scripts/claim/claim.js (tested in ci.yml).
+name: Claim
+
+on:
+  issue_comment:
+    types: [created]
+  schedule:
+    - cron: '17 5 * * *'
+  workflow_dispatch:
+
+permissions:
+  contents: read # to check out scripts/claim
+  issues: write
+  pull-requests: read
+
+# One run at a time per issue, so two simultaneous /claim comments can't both win.
+concurrency:
+  group: claim-${{ github.event.issue.number || 'sweep' }}
+  cancel-in-progress: false
+
+jobs:
+  claim:
+    name: Claim bot
+    runs-on: ubuntu-24.04
+    timeout-minutes: 10
+    if: >-
+      github.event_name != 'issue_comment' ||
+      (!github.event.issue.pull_request && github.event.comment.user.type != 'Bot' &&
+      (startsWith(github.event.comment.body, '/claim') || startsWith(github.event.comment.body, '/unclaim')))
+    steps:
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          sparse-checkout: scripts/claim
+      - uses: actions/github-script@3a2844b7e9c422d3c10d287c895573f7108da1b3 # v9.0.0
+        with:
+          script: |
+            const claim = require('./scripts/claim/claim.js');
+            if (context.eventName === 'issue_comment') {
+              await claim.handleComment({ github, context });
+            } else {
+              const released = await claim.sweep({ github, context });
+              core.info(`Released: ${released.join(', ') || 'none'}`);
+            }