feat: add audio dataset pipeline skeleton

nodes/selva_dataset_pipeline.py

@@ -0,0 +1,26 @@
+"""SelVA Audio Dataset Pipeline — chainable in-memory preprocessing nodes.
+
+Typical chain:
+  SelvaDatasetLoader
+      ↓ AUDIO_DATASET
+  SelvaDatasetResampler       (optional)
+      ↓ AUDIO_DATASET
+  SelvaDatasetLUFSNormalizer  (optional)
+      ↓ AUDIO_DATASET
+  SelvaDatasetInspector       (optional)
+      ↓ AUDIO_DATASET  +  STRING report
+  SelvaDatasetItemExtractor   → AUDIO (bridges to save/preview nodes)
+"""
+
+from pathlib import Path
+
+import numpy as np
+import torch
+import torchaudio
+
+from .utils import SELVA_CATEGORY
+
+# ComfyUI custom type name — passed between all dataset pipeline nodes
+AUDIO_DATASET = "AUDIO_DATASET"
+
+_AUDIO_EXTS = {".wav", ".flac", ".mp3", ".ogg", ".aac", ".m4a"}