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/main.py

@@ -50,6 +50,23 @@ import sys
 from pathlib import Path
 from typing import Optional
 
+def _require_tty(command_name: str) -> None:
+    """Exit with a clear error if stdin is not a terminal.
+
+    Interactive TUI commands (hermes tools, hermes setup, hermes model) use
+    curses or input() prompts that spin at 100% CPU when stdin is a pipe.
+    This guard prevents accidental non-interactive invocation.
+    """
+    if not sys.stdin.isatty():
+        print(
+            f"Error: 'hermes {command_name}' requires an interactive terminal.\n"
+            f"It cannot be run through a pipe or non-interactive subprocess.\n"
+            f"Run it directly in your terminal instead.",
+            file=sys.stderr,
+        )
+        sys.exit(1)
+
+
 # Add project root to path
 PROJECT_ROOT = Path(__file__).parent.parent.resolve()
 sys.path.insert(0, str(PROJECT_ROOT))
@@ -617,6 +634,7 @@ def cmd_gateway(args):
 
 def cmd_whatsapp(args):
     """Set up WhatsApp: choose mode, configure, install bridge, pair via QR."""
+    _require_tty("whatsapp")
     import subprocess
     from pathlib import Path
     from hermes_cli.config import get_env_value, save_env_value
@@ -803,12 +821,14 @@ def cmd_whatsapp(args):
 
 def cmd_setup(args):
     """Interactive setup wizard."""
+    _require_tty("setup")
     from hermes_cli.setup import run_setup_wizard
     run_setup_wizard(args)
 
 
 def cmd_model(args):
     """Select default model — starts with provider selection, then model picker."""
+    _require_tty("model")
     from hermes_cli.auth import (
         resolve_provider, AuthError, format_auth_error,
     )
@@ -2459,6 +2479,7 @@ def cmd_version(args):
 
 def cmd_uninstall(args):
     """Uninstall Hermes Agent."""
+    _require_tty("uninstall")
     from hermes_cli.uninstall import run_uninstall
     run_uninstall(args)
 
@@ -4131,6 +4152,7 @@ For more help on a command:
     def cmd_skills(args):
         # Route 'config' action to skills_config module
         if getattr(args, 'skills_action', None) == 'config':
+            _require_tty("skills config")
             from hermes_cli.skills_config import skills_command as skills_config_command
             skills_config_command(args)
         else:
@@ -4341,6 +4363,7 @@ For more help on a command:
             from hermes_cli.tools_config import tools_disable_enable_command
             tools_disable_enable_command(args)
         else:
+            _require_tty("tools")
             from hermes_cli.tools_config import tools_command
             tools_command(args)