feat: add voice mode with push-to-talk and TTS output for CLI

Implements Issue #314 Phase 2 & 3:
- /voice command to toggle voice mode (on/off/tts/status)
- Ctrl+Space push-to-talk recording via sounddevice
- Whisper STT transcription via existing transcription_tools
- Optional TTS response playback via existing tts_tool
- Visual indicators in prompt (recording/transcribing/voice)
- 21 unit tests, all mocked (no real mic/API)
- Optional deps: sounddevice, numpy (pip install hermes-agent[voice])

pyproject.toml

@@ -48,6 +48,7 @@ cron = ["croniter"]
 slack = ["slack-bolt>=1.18.0", "slack-sdk>=3.27.0"]
 cli = ["simple-term-menu"]
 tts-premium = ["elevenlabs"]
+voice = ["sounddevice>=0.4.6", "numpy>=1.24.0"]
 pty = [
   "ptyprocess>=0.7.0; sys_platform != 'win32'",
   "pywinpty>=2.0.0; sys_platform == 'win32'",
@@ -78,6 +79,7 @@ all = [
   "hermes-agent[mcp]",
   "hermes-agent[homeassistant]",
   "hermes-agent[acp]",
+  "hermes-agent[voice]",
 ]
 
 [project.scripts]