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/checklist.py

@@ -5,6 +5,7 @@ toggleable list of items.  Falls back to a numbered text UI when
 curses is unavailable (Windows without curses, piped stdin, etc.).
 """
 
+import sys
 from typing import List, Set
 
 from hermes_cli.colors import Colors, color
@@ -26,6 +27,10 @@ def curses_checklist(
         The indices the user confirmed as checked.  On cancel (ESC/q),
         returns ``pre_selected`` unchanged.
     """
+    # Safety: return defaults when stdin is not a terminal.
+    if not sys.stdin.isatty():
+        return set(pre_selected)
+
     try:
         import curses
         selected = set(pre_selected)