ci(coverage): run the coverage job weekly and on request, not on every push

.github/workflows/test-coverage.yaml

@@ -1,24 +1,28 @@
 # Workflow derived from https://github.com/r-lib/actions/tree/v2/examples
 # Need help debugging build failures? Start at https://github.com/r-lib/actions#where-to-find-help
+# Coverage runs weekly and on request, not on every push: under covr the
+# every-run tier takes about an hour on the 2-core runner, and in October 2026
+# the hosted runner was recycled mid-job ("runner has received a shutdown
+# signal") on every push-triggered run. The test jobs on every push are
+# fast-checks.yaml and R-CMD-check.yaml.
 on:
-  push:
-    branches: [main, develop]
-    # Review-record commits touch dev/ only and cannot change any test
-    # outcome, so they do not launch package CI (F-102).
-    paths-ignore: ['dev/**']
-  pull_request:
-    branches: [main, develop]
+  schedule:
+    - cron: '0 6 * * 0'  # Sundays 06:00 UTC, after the weekly certification
+  workflow_dispatch:
 
 name: test-coverage
 
 jobs:
   test-coverage:
     runs-on: ubuntu-latest
+    timeout-minutes: 90
     env:
       GITHUB_PAT: ${{ secrets.GITHUB_TOKEN }}
 
     steps:
       - uses: actions/checkout@v4
+        with:
+          ref: ${{ github.event_name == 'schedule' && 'develop' || github.ref }}
 
       - uses: r-lib/actions/setup-r@v2
         with: