fix: auto-reload MCP tools when mcp_servers config changes without restart

Fixes #1036

After adding an MCP server to config.yaml, users had to restart Hermes
before the new tools became visible — even though /reload-mcp existed.

Add _check_config_mcp_changes() called from process_loop every 5s:
- stat() config.yaml for mtime changes (fast path, no YAML parse)
- On mtime change, parse and compare mcp_servers section
- If mcp_servers changed, auto-trigger _reload_mcp() and notify user
- Skip check while agent is running to avoid interrupting tool calls
- Throttled to CONFIG_WATCH_INTERVAL=5s to avoid busy-polling

/reload-mcp still works for manual force-reload.

Tests: 6 new tests in TestMCPConfigWatch, all passed

cli.py

@@ -3484,6 +3484,56 @@ class HermesCLI:
         except Exception as e:
             print(f"  Error generating insights: {e}")
 
+    def _check_config_mcp_changes(self) -> None:
+        """Detect mcp_servers changes in config.yaml and auto-reload MCP connections.
+
+        Called from process_loop every CONFIG_WATCH_INTERVAL seconds.
+        Compares config.yaml mtime + mcp_servers section against the last
+        known state.  When a change is detected, triggers _reload_mcp() and
+        informs the user so they know the tool list has been refreshed.
+        """
+        import time
+        import yaml as _yaml
+
+        CONFIG_WATCH_INTERVAL = 5.0  # seconds between config.yaml stat() calls
+
+        now = time.monotonic()
+        if now - self._last_config_check < CONFIG_WATCH_INTERVAL:
+            return
+        self._last_config_check = now
+
+        from hermes_cli.config import get_config_path as _get_config_path
+        cfg_path = _get_config_path()
+        if not cfg_path.exists():
+            return
+
+        try:
+            mtime = cfg_path.stat().st_mtime
+        except OSError:
+            return
+
+        if mtime == self._config_mtime:
+            return  # File unchanged — fast path
+
+        # File changed — check whether mcp_servers section changed
+        self._config_mtime = mtime
+        try:
+            with open(cfg_path, encoding="utf-8") as f:
+                new_cfg = _yaml.safe_load(f) or {}
+        except Exception:
+            return
+
+        new_mcp = new_cfg.get("mcp_servers") or {}
+        if new_mcp == self._config_mcp_servers:
+            return  # mcp_servers unchanged (some other section was edited)
+
+        self._config_mcp_servers = new_mcp
+        # Notify user and reload
+        print()
+        print("🔄 MCP server config changed — reloading connections...")
+        with self._busy_command(self._slow_command_status("/reload-mcp")):
+            self._reload_mcp()
+
     def _reload_mcp(self):
         """Reload MCP servers: disconnect all, re-read config.yaml, reconnect.
 
@@ -4749,6 +4799,12 @@ class HermesCLI:
         self._interrupt_queue = queue.Queue()   # For messages typed while agent is running
         self._should_exit = False
         self._last_ctrl_c_time = 0  # Track double Ctrl+C for force exit
+        # Config file watcher — detect mcp_servers changes and auto-reload
+        from hermes_cli.config import get_config_path as _get_config_path
+        _cfg_path = _get_config_path()
+        self._config_mtime: float = _cfg_path.stat().st_mtime if _cfg_path.exists() else 0.0
+        self._config_mcp_servers: dict = self.config.get("mcp_servers") or {}
+        self._last_config_check: float = 0.0  # monotonic time of last check
 
         # Clarify tool state: interactive question/answer with the user.
         # When the agent calls the clarify tool, _clarify_state is set and
@@ -5682,6 +5738,9 @@ class HermesCLI:
                     try:
                         user_input = self._pending_input.get(timeout=0.1)
                     except queue.Empty:
+                        # Periodic config watcher — auto-reload MCP on mcp_servers change
+                        if not self._agent_running:
+                            self._check_config_mcp_changes()
                         continue
                     
                     if not user_input: