fix: add plugin root to sys.path so prismaudio_core is importable

ComfyUI does not add the custom node directory to sys.path automatically,
so prismaudio_core (a package inside the plugin dir) was not found at runtime.

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

__init__.py

@@ -1,6 +1,10 @@
 """
 ComfyUI-PrismAudio: Video-to-Audio and Text-to-Audio generation using PrismAudio (ICLR 2026).
 """
+import sys
+import os
+sys.path.insert(0, os.path.dirname(__file__))
+
 from .nodes import NODE_CLASS_MAPPINGS, NODE_DISPLAY_NAME_MAPPINGS
 
 __all__ = ["NODE_CLASS_MAPPINGS", "NODE_DISPLAY_NAME_MAPPINGS"]