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/ext/bigvgan/bigvgan.py

@@ -0,0 +1,32 @@
+from pathlib import Path
+
+import torch
+import torch.nn as nn
+from omegaconf import OmegaConf
+
+from selva_core.ext.bigvgan.models import BigVGANVocoder
+
+_bigvgan_vocoder_path = Path(__file__).parent / 'bigvgan_vocoder.yml'
+
+
+class BigVGAN(nn.Module):
+
+    def __init__(self, ckpt_path, config_path=_bigvgan_vocoder_path):
+        super().__init__()
+        vocoder_cfg = OmegaConf.load(config_path)
+        self.vocoder = BigVGANVocoder(vocoder_cfg).eval()
+        vocoder_ckpt = torch.load(ckpt_path, map_location='cpu', weights_only=True)['generator']
+        self.vocoder.load_state_dict(vocoder_ckpt)
+
+        self.weight_norm_removed = False
+        self.remove_weight_norm()
+
+    @torch.inference_mode()
+    def forward(self, x):
+        assert self.weight_norm_removed, 'call remove_weight_norm() before inference'
+        return self.vocoder(x)
+
+    def remove_weight_norm(self):
+        self.vocoder.remove_weight_norm()
+        self.weight_norm_removed = True
+        return self