fix: add missing subprocess import in _install_neutts_deps

The function uses subprocess.run() and subprocess.CalledProcessError but
never imported the module. This caused a NameError crash during setup
when users selected NeuTTS as their TTS provider.

Fixes #1698

hermes_cli/setup.py

@@ -1633,6 +1633,7 @@ def _check_espeak_ng() -> bool:
 
 def _install_neutts_deps() -> bool:
     """Install NeuTTS dependencies with user approval. Returns True on success."""
+    import subprocess
     import sys
 
     # Check espeak-ng