Fix HunyuanFoley xregen: register model lib sys.path in main process

ZeroGPU workers add model library dirs to sys.path via _ensure_syspath,
but this only affects the worker subprocess. When the worker pickles its
return value (which contains hunyuanvideo_foley objects like text_feats),
_ForkingPickler.loads() in the main process fails with:
ModuleNotFoundError: No module named 'hunyuanvideo_foley'

Fix: call _ensure_syspath for all three model libraries at module level
(immediately after the function definition) so the main process has all
model paths in sys.path before it ever deserialises a worker result.

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

app.py

@@ -173,6 +173,16 @@ def _ensure_syspath(subdir: str) -> str:
         sys.path.insert(0, p)
     return p
 
+# Ensure all model library subdirs are in sys.path for the MAIN PROCESS.
+# ZeroGPU workers also call _ensure_syspath internally, but when the worker
+# pickles its return value and the main process deserialises it via
+# _ForkingPickler.loads(), the main process must already have these modules
+# importable — otherwise ModuleNotFoundError is raised during unpickling.
+_ensure_syspath("HunyuanVideo-Foley")
+_ensure_syspath("MMAudio")
+_ensure_syspath("TARO")
+print("[startup] Model library sys.path entries registered in main process.")
+
 
 def _get_device_and_dtype() -> tuple:
     """Return (device, weight_dtype) pair used by all GPU functions.