fix(ci): restore broken YAML structure in 3 workflows, revert aggressive STALE_HOURS

- pr-auto-response.yml: restore permissions, steps, and checkout in
  contributor-tier-issues job (broken by runner swap)
- pr-check-stale.yml: restore steps block and step name
- pr-intake-checks.yml: restore steps block, checkout, and timeout
- pr-check-status.yml: revert STALE_HOURS from 4 to 48 (not a cost
  optimization; 4h is too aggressive), switch to ubuntu-latest per
  PR description

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

.github/workflows/pr-intake-checks.yml

@@ -17,6 +17,12 @@ jobs:
     intake:
         name: Intake Checks
         runs-on: ubuntu-latest
+        timeout-minutes: 10
+        steps:
+            - name: Checkout repository
+              uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4
+
+            - name: Run safe PR intake checks
               uses: actions/github-script@ed597411d8f924073f98dfc5c65a23a2325f34cd # v8
               with:
                   script: |