fix: Fail-closed pinned resolver, close session on HA stop, drop dead workflow step

- _PinnedResolver raises on unpinned hosts instead of falling back to
  live DNS: nothing legitimate resolves other hosts on a pinned session
  (redirects are off), so fail closed
- dedicated session is also closed on EVENT_HOMEASSISTANT_CLOSE: core
  stop does not unload entries, and the raw ClientSession has no HA
  auto-cleanup, which left 'Unclosed client session' logs at shutdown
- hassfest.yaml: remove the version-print step, hassfest runs inside
  the action's docker image and is never on the runner PATH

.github/workflows/hassfest.yaml

@@ -35,11 +35,6 @@ jobs:
       - name: Run hassfest validation
         uses: home-assistant/actions/hassfest@master
 
-      - name: Print hassfest version
-        if: always()
-        run: |
-          echo "Hassfest version: $(hassfest --version)"
-
     concurrency:
       group: ${{ github.workflow }}-${{ github.ref }}
       cancel-in-progress: true