feat: auto-close inactive merge-conflicted PRs

.github/workflows/stale-merge-conflicts.yml

@@ -0,0 +1,58 @@
+name: Close stale merge-conflicted PRs
+
+on:
+  schedule:
+    - cron: "17 2 * * *"
+  workflow_dispatch:
+
+permissions:
+  contents: read
+  issues: write
+  pull-requests: write
+
+jobs:
+  stale-merge-conflicts:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Warn and close inactive merge-conflicted PRs
+        uses: actions/stale@v10
+        with:
+          repo-token: ${{ secrets.GITHUB_TOKEN }}
+
+          # Do not process issues.
+          days-before-issue-stale: -1
+          days-before-issue-close: -1
+
+          # Only process PRs that still have unresolved merge conflicts.
+          only-pr-labels: "PR has merge conflicts"
+
+          # Warn after 30 inactive days, then close after 5 more inactive days.
+          days-before-pr-stale: 30
+          days-before-pr-close: 5
+
+          # Use a separate stale label so the original merge-conflict label keeps its meaning.
+          stale-pr-label: "stale merge conflict"
+          close-pr-label: "closed stale merge conflict"
+
+          # If the contributor comments or updates the PR, remove stale state and restart the timer.
+          remove-pr-stale-when-updated: true
+
+          # Help process larger backlogs across daily runs.
+          operations-per-run: 100
+
+          stale-pr-message: |
+            ⚠️ **This PR still has unresolved merge conflicts and has been inactive for the past 30 days.**
+
+            The `PR has merge conflicts` label is still applied, and there has been no recent activity on this PR.
+
+            Please resolve the merge conflicts or leave a comment if you are still actively working on it.
+
+            If there is no further activity within the next 5 days, this PR may be automatically closed to help keep the PR backlog manageable.
+
+          close-pr-message: |
+            🔒 **Closing this PR due to unresolved merge conflicts and prolonged inactivity.**
+
+            This PR still had unresolved merge conflicts, and there was no activity within 5 days of the stale warning being posted.
+
+            You may reopen this PR or submit a new one after resolving the merge conflicts.