fix(cli): import file_signature in TUI run-state init

#111408 widened the MCP config watcher seed from mtime to
utils.file_signature but omitted the import in cli_tui_mixin.
The NameError only fires when config.yaml exists, so isolated-home
tests short-circuited past it and every real CLI launch crashed.

Signed-off-by: mr-r0b0t <adam.manning@gmail.com>

hermes_cli/cli_tui_mixin.py

@@ -1818,6 +1818,7 @@ class CLITuiMixin:
 
         # Config file watcher — detect mcp_servers changes and auto-reload.
         from hermes_cli.config import get_config_path as _get_config_path
+        from utils import file_signature
         _cfg_path = _get_config_path()
         self._config_sig: tuple | None = file_signature(_cfg_path.stat()) if _cfg_path.exists() else None
         self._config_mcp_servers: dict = self.config.get("mcp_servers") or {}

tests/hermes_cli/test_cli_mcp_config_watch.py

@@ -195,6 +195,29 @@ class TestMCPConfigWatch:
         assert "MCP server config changed" not in capsys.readouterr().out
 
 
+def test_tui_init_run_state_seeds_config_sig_when_config_exists(monkeypatch):
+    """REPL init must seed _config_sig from on-disk config.yaml.
+
+    file_signature is only evaluated when the file exists (short-circuit
+    otherwise). Isolated-home tests without a config file therefore never
+    exercised the call, and a missing import crashed every real CLI launch.
+    """
+    from hermes_cli.config import get_config_path
+    import cli as cli_mod
+
+    monkeypatch.setenv("HERMES_DEFER_AGENT_STARTUP", "1")
+    cfg_file = get_config_path()
+    cfg_file.parent.mkdir(parents=True, exist_ok=True)
+    cfg_file.write_text("mcp_servers: {}\n")
+
+    obj = object.__new__(cli_mod.HermesCLI)
+    obj.config = {"mcp_servers": {}}
+    obj._tui_init_run_state()
+
+    assert obj._config_sig == file_signature(cfg_file.stat())
+    assert obj._config_mcp_servers == {}
+
+
 def test_pinned_mtime_same_size_replacement_triggers_reload(tmp_path):
     """#111105: cp -p / rsync -t style replacement (same mtime, same size) must still reload."""
     import os