Add WanVideo Save Merged Model node from Comfyui_WW_msave

Consolidates the WanVideoSaveMergedModel node into this project as
save_node.py. Saves WanVideo diffusion models (with merged LoRAs) as
safetensors files with metadata for traceability.

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

__init__.py

@@ -1,3 +1,10 @@
 from .nodes import NODE_CLASS_MAPPINGS, NODE_DISPLAY_NAME_MAPPINGS
+from .save_node import (
+    NODE_CLASS_MAPPINGS as SAVE_CLASS_MAPPINGS,
+    NODE_DISPLAY_NAME_MAPPINGS as SAVE_DISPLAY_MAPPINGS,
+)
+
+NODE_CLASS_MAPPINGS.update(SAVE_CLASS_MAPPINGS)
+NODE_DISPLAY_NAME_MAPPINGS.update(SAVE_DISPLAY_MAPPINGS)
 
 __all__ = ["NODE_CLASS_MAPPINGS", "NODE_DISPLAY_NAME_MAPPINGS"]