ci(mobile): merge the Android APK download bump on the site after its checks pass (#29981)

.github/workflows/mobile-android-release.yml

@@ -275,7 +275,7 @@ jobs:
           path: site
           token: ${{ steps.app-token.outputs.token }}
 
-      - name: Open the version bump PR
+      - name: Open and merge the version bump PR
         working-directory: site
         env:
           GH_TOKEN: ${{ steps.app-token.outputs.token }}
@@ -303,6 +303,26 @@ jobs:
           fi
           echo "Android APK download bump: $pr" >> "$GITHUB_STEP_SUMMARY"
 
+          # Why wait for checks: they push a deploy commit onto the branch (merging first fails with
+          # "Head branch was modified"), and a failed site build must not merge. Main's push deploys.
+          sleep 20
+          gh pr checks "$pr" --repo "$SITE_REPO" --watch --interval 15 || true
+          failed="$(gh pr checks "$pr" --repo "$SITE_REPO" --json bucket --jq 'map(select(.bucket == "fail")) | length' 2>/dev/null || true)"
+          # The deploy commit is [skip ci], so the final head may report no checks at all.
+          if [ "${failed:-0}" != "0" ]; then
+            echo "::warning::The site's checks failed on $pr; not merging. Fix and merge it by hand."
+            exit 1
+          fi
+          for _ in 1 2 3; do
+            if gh pr merge "$pr" --repo "$SITE_REPO" --squash --delete-branch; then
+              echo "Merged; the site deploys from main." >> "$GITHUB_STEP_SUMMARY"
+              exit 0
+            fi
+            sleep 30
+          done
+          echo "::warning::Could not merge $pr; merge it by hand to update /download/android."
+          exit 1
+
       - name: Report a failed bump
         if: failure()
         run: |