fix: add TTY guard to interactive CLI commands to prevent CPU spin (#3933)

When interactive TUI commands are invoked non-interactively (e.g. via
the agent's terminal() tool through a subprocess pipe), curses loops
spin at 100% CPU and input() calls hang indefinitely.

Defense in depth — two layers:

1. Source-level guard in curses_checklist() (curses_ui.py + checklist.py):
   Returns cancel_returns immediately when stdin is not a TTY. This
   catches ALL callers automatically, including future code.

2. Command-level guards with clear error messages:
   - hermes tools (interactive checklist, not list/disable/enable)
   - hermes setup (interactive wizard)
   - hermes model (provider/model picker)
   - hermes whatsapp (pairing setup)
   - hermes skills config (skill toggle)
   - hermes mcp configure (tool selection)
   - hermes uninstall (confirmation prompt)

Non-interactive subcommands (hermes tools list, hermes tools enable,
hermes mcp add/remove/list/test, hermes skills search/install/browse)
remain unaffected.

hermes_cli/mcp_config.py

@@ -511,6 +511,10 @@ def _interpolate_value(value: str) -> str:
 
 def cmd_mcp_configure(args):
     """Reconfigure which tools are enabled for an existing MCP server."""
+    import sys as _sys
+    if not _sys.stdin.isatty():
+        print("Error: 'hermes mcp configure' requires an interactive terminal.", file=_sys.stderr)
+        _sys.exit(1)
     name = args.name
     servers = _get_mcp_servers()