ci(github): add stale issue workflow (dry-run)

.github/ci-overview.md

@@ -57,6 +57,7 @@ via composite actions and reusable workflows. Python helpers in `scripts/` are i
 | `crowdin.yml`, `lupdate.yml` | Translation workflows |
 | `dependency-review.yml` | Dependency security review |
 | `scorecard.yml` | OpenSSF Scorecard |
+| `stale.yml` | Nightly stale-issue labeling and closing (feature requests get their own close message) |
 | `flatpak.yml` | Flatpak builds |
 | `mirror-gstreamer.yml` | Mirror upstream GStreamer releases to the QGC S3 bucket |
 | `px4-metadata.yml` | PX4 metadata sync |

.github/workflows/stale.yml

@@ -0,0 +1,93 @@
+name: Stale Issues
+
+on:
+  schedule:
+    - cron: '30 1 * * *'
+  workflow_dispatch:
+
+concurrency:
+  group: ${{ github.workflow }}
+  cancel-in-progress: false
+
+permissions: {}
+
+jobs:
+  stale-issues:
+    name: Stale Issues (non-feature)
+    runs-on: ubuntu-latest
+    timeout-minutes: 30
+    permissions:
+      issues: write
+      # Required to reset the Actions cache entry that persists resume state between capped runs.
+      actions: write
+
+    steps:
+      - name: Harden Runner
+        uses: step-security/harden-runner@v2
+        with:
+          egress-policy: audit
+
+      - name: Mark and close stale issues
+        uses: actions/stale@v11
+        with:
+          # Remove debug-only once the dry-run output has been reviewed.
+          debug-only: true
+          days-before-issue-stale: 90
+          days-before-issue-close: 30
+          days-before-pr-stale: -1
+          days-before-pr-close: -1
+          remove-pr-stale-when-updated: false
+          stale-issue-label: stale
+          exempt-issue-labels: 'Priority: Critical,Feature Request'
+          exempt-all-issue-milestones: true
+          remove-issue-stale-when-updated: true
+          ascending: true
+          # Dry run: state is not persisted in debug mode, so the cap must cover the whole backlog.
+          # Lower to 400 when going live: two jobs share the 1000 req/hr GITHUB_TOKEN budget.
+          operations-per-run: 1500
+          # Empty message labels silently to avoid a notification flood on the initial backlog sweep.
+          stale-issue-message: ''
+          close-issue-message: >
+            This issue was automatically closed after 120 days of inactivity. It most likely refers
+            to a version of QGroundControl that is no longer current. If it is still relevant on the
+            latest Stable or Daily build, please reopen or file a new issue including the QGC version,
+            firmware (PX4/ArduPilot) and version, platform, and steps to reproduce.
+
+  stale-features:
+    name: Stale Feature Requests
+    runs-on: ubuntu-latest
+    timeout-minutes: 30
+    needs: stale-issues
+    permissions:
+      issues: write
+      actions: write
+
+    steps:
+      - name: Harden Runner
+        uses: step-security/harden-runner@v2
+        with:
+          egress-policy: audit
+
+      - name: Mark and close stale feature requests
+        uses: actions/stale@v11
+        with:
+          # Remove debug-only once the dry-run output has been reviewed.
+          debug-only: true
+          days-before-issue-stale: 90
+          days-before-issue-close: 30
+          days-before-pr-stale: -1
+          days-before-pr-close: -1
+          remove-pr-stale-when-updated: false
+          stale-issue-label: stale
+          any-of-issue-labels: 'Feature Request'
+          exempt-issue-labels: 'Priority: Critical'
+          exempt-all-issue-milestones: true
+          remove-issue-stale-when-updated: true
+          ascending: true
+          # Lower to 400 when going live (see stale-issues).
+          operations-per-run: 1500
+          # Empty message labels silently to avoid a notification flood on the initial backlog sweep.
+          stale-issue-message: ''
+          close-issue-message: >
+            This feature request was automatically closed after 120 days of inactivity. If there is
+            still interest, please reopen or start a GitHub Discussion so it can be reconsidered.