fix(resume): auto-create session entry in update_yaml_resumed.sh when missing

.agents/skills/multi-agent-mux-resume/scripts/update_yaml_resumed.sh

@@ -84,8 +84,22 @@ for s in d.get('herdr_sessions', []):
         break
 
 if target is None:
-    print(f"ERROR: session not in YAML: {name}", flush=True)
-    raise SystemExit(1)
+    ws_root = os.environ.get('WORKSPACE_ROOT', '')
+    server_name = os.environ.get('HERDR_SERVER_NAME', 'multi-agent-mux')
+    target = {
+        'name': name,
+        'status': 'running',
+        'role': 'creator',
+        'herdr_session_created_at': now,
+        'herdr_session_epoch': int(os.environ.get('NOW_EPOCH', '0') or '0'),
+        'herdr_server': server_name,
+        'delegate_job_id': None,
+        'pane': {'index': 0, 'pid': int(pane_pid) if pane_pid.isdigit() else 0, 'cmd': agent, 'cwd': ws_root},
+        'start_command': f'HERDR_SERVER_NAME={server_name} herdr agent attach {name}',
+        'attach_command': f'HERDR_SERVER_NAME={server_name} herdr agent attach {name}',
+        'kill_command': f'HERDR_SERVER_NAME={server_name} herdr kill-session -t {name}',
+    }
+    d.setdefault('herdr_sessions', []).append(target)
 
 target['status'] = 'running'
 target.pop('terminated_at', None)