Pin transformers<4.40.0 for PyTorch 2.1 compatibility

transformers 4.40+ uses serialized_type_name kwarg in _register_pytree_node()
which doesn't exist in PyTorch 2.1. Pin to older version.

Also removes the ineffective pytree shim.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

main.py

@@ -16,20 +16,6 @@ os.chdir(PROJECT_ROOT)
 # Add project root to path
 sys.path.insert(0, str(PROJECT_ROOT))
 
-# PyTorch pytree compatibility shim for AudioCraft
-# The API changed between PyTorch versions:
-#   - Older: _register_pytree_node (private, with underscore)
-#   - Newer: register_pytree_node (public, without underscore)
-# Create aliases in both directions to support any version
-try:
-    import torch.utils._pytree as _pytree
-    if hasattr(_pytree, '_register_pytree_node') and not hasattr(_pytree, 'register_pytree_node'):
-        _pytree.register_pytree_node = _pytree._register_pytree_node
-    if hasattr(_pytree, 'register_pytree_node') and not hasattr(_pytree, '_register_pytree_node'):
-        _pytree._register_pytree_node = _pytree.register_pytree_node
-except Exception:
-    pass  # Ignore if torch not installed or patch fails
-
 from config.settings import get_settings
 from src.core.gpu_manager import GPUMemoryManager
 from src.core.model_registry import ModelRegistry

requirements.txt

@@ -1,9 +1,13 @@
-# Core ML - Pin to AudioCraft-compatible versions (2.4+ breaks pytree API)
+# Core ML - Pin to AudioCraft-compatible versions
 torch>=2.1.0,<2.4.0
 torchaudio>=2.1.0,<2.4.0
 audiocraft>=1.3.0
 xformers>=0.0.22
 
+# Pin transformers to version compatible with PyTorch 2.1
+# Newer versions use serialized_type_name kwarg not in PyTorch 2.1
+transformers>=4.30.0,<4.40.0
+
 # UI
 gradio>=4.0.0