Add OmniVoice Voice Preset node with two female voice samples

Two built-in presets, auto-downloaded and cached to ComfyUI/models/omnivoice/presets/:
- "Nature – female, warm" (F5-TTS basic_ref_en.wav, transcript included)
- "Shadowheart – female, expressive" (Chatterbox demo, connect Whisper for transcript)

Outputs ref_audio (AUDIO) and ref_text (STRING) — wire directly into
OmniVoice Generate. Updated default workflow to use this node.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

__init__.py

@@ -1,15 +1,17 @@
-from .nodes import OmniVoiceModelLoader, OmniVoiceGenerate, OmniVoiceEpubLoader
+from .nodes import OmniVoiceModelLoader, OmniVoiceGenerate, OmniVoiceEpubLoader, OmniVoiceVoicePreset
 
 NODE_CLASS_MAPPINGS = {
     "OmniVoiceModelLoader": OmniVoiceModelLoader,
     "OmniVoiceGenerate": OmniVoiceGenerate,
     "OmniVoiceEpubLoader": OmniVoiceEpubLoader,
+    "OmniVoiceVoicePreset": OmniVoiceVoicePreset,
 }
 
 NODE_DISPLAY_NAME_MAPPINGS = {
     "OmniVoiceModelLoader": "OmniVoice Model Loader",
     "OmniVoiceGenerate": "OmniVoice Generate",
     "OmniVoiceEpubLoader": "OmniVoice EPUB Loader",
+    "OmniVoiceVoicePreset": "OmniVoice Voice Preset",
 }
 
 __all__ = ["NODE_CLASS_MAPPINGS", "NODE_DISPLAY_NAME_MAPPINGS"]