chore: vendor selva_core from jnwnlee/selva@d7d40a9

Pure PyTorch SelVA source for SelvaModelLoader/FeatureExtractor/Sampler nodes.
Imports rewritten from selva.* to selva_core.*. mel_converter.py: replaced
librosa.filters.mel with pure-numpy implementation to avoid librosa→numba→NumPy
version incompatibility in some ComfyUI environments.

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

selva_core/model/utils/factory.py

@@ -0,0 +1,18 @@
+import torch
+
+from selva_core.utils.misc import instantiate_from_config
+from selva_core.model.networks_video_enc import TextSynch as TextSynchVideoEnc
+from selva_core.model.networks_generator import MMAudio
+
+
+_MODEL_ZOO = (TextSynchVideoEnc, MMAudio)
+
+
+def create_model_from_factory(factory_path: str, name: str, **kwargs) -> torch.nn.Module:
+    """
+    Dynamically imports and calls a model factory function.
+    """
+    params = {'name': name, **kwargs}
+    model = instantiate_from_config(factory_path, params)
+    assert isinstance(model, _MODEL_ZOO), f"Model {type(model)} is not a valid model type."
+    return model