Add daily continuous runs of all our supported release branches

PiperOrigin-RevId: 674469632

.github/workflows/staleness_check.yml

@@ -23,6 +23,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
+        # TODO Remove this parameterization once the release branch testing is stable.
         branch: [main, 25.x, 27.x, 28.x]
         os: [{ name: Linux, value: ubuntu-latest}]
         exclude:

.github/workflows/test_release_branches.yml

@@ -0,0 +1,25 @@
+name: Release Branch Tests
+
+on:
+  schedule:
+    # Run daily at 10 AM UTC (2 AM PDT)
+    - cron: 0 10 * * *
+  workflow_dispatch:
+
+permissions: {}
+
+jobs:
+  releases:
+    strategy:
+      fail-fast: false
+      matrix:
+        branch: [25.x, 27.x, 28.x]
+    runs-on: ubuntu-latest
+    permissions:
+      actions: write
+    env:
+      GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+      GH_REPO: ${{ github.repository }}
+    name: Run Tests on ${{ matrix.branch }}
+    steps:
+      - run: gh workflow run test_runner.yml --ref ${{ matrix.branch }}