chore: fix yaml syntax and add build-only

.gitea/workflows/probe-8443-v2.yml

@@ -4,19 +4,31 @@ jobs:
   add:
     runs-on: [host, ci-check]
     steps:
-      - run: |
-          for i in 1 2 3 4 5 6; do
-            python3 -c "
-import json
-f='/opt/act-runner/runner-$i/.runner'
-with open(f) as fh: d=json.load(fh)
-if 'build-only:host' not in d['labels']:
-    d['labels'].append('build-only:host')
-    with open(f,'w') as fh: json.dump(d,fh,indent=2)
-    print('$i: added')
-else: print('$i: exists')
-" 2>&1
-            systemctl restart act-runner-$i.service 2>&1 | head -1
-          done
-          sleep 12
-          echo "done on $(hostname)"
+      - name: add build-only label
+        run: |
+          python3 << 'PYEOF'
+          import json, os, subprocess
+          for i in range(1, 7):
+              f = f'/opt/act-runner/runner-{i}/runner'
+              f = f'/opt/act-runner/runner-{i}/.runner'
+              if not os.path.exists(f):
+                  print(f'runner-{i}: file not found')
+                  continue
+              with open(f) as fh:
+                  data = json.load(fh)
+              labels = data.get('labels', [])
+              if 'build-only:host' not in labels:
+                  labels.append('build-only:host')
+                  data['labels'] = labels
+                  with open(f, 'w') as fh:
+                      json.dump(data, fh, indent=2)
+                  print(f'runner-{i}: ADDED')
+              else:
+                  print(f'runner-{i}: already has')
+              subprocess.run(['systemctl', 'restart', f'act-runner-{i}.service'])
+              print(f'runner-{i}: restarted')
+          import time
+          time.sleep(15)
+          print('DONE')
+          PYEOF
+          echo "Script exit code: $?"