feat: add audio_scan module with build_profile

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

core/audio_scan.py

@@ -0,0 +1,40 @@
+"""Audio similarity scanning — MFCC-based profile matching."""
+
+import numpy as np
+import librosa
+
+from .paths import _log
+
+_N_MFCC = 20
+_SR = 22050
+
+
+def _extract_mfcc(path: str, sr: int = _SR) -> np.ndarray:
+    """Load audio from a file and return a mean MFCC vector (20-dim)."""
+    y, _ = librosa.load(path, sr=sr, mono=True)
+    mfcc = librosa.feature.mfcc(y=y, sr=sr, n_mfcc=_N_MFCC)
+    return mfcc.mean(axis=1)  # average over time → (20,)
+
+
+def build_profile(clip_paths: list[str]) -> dict | None:
+    """Extract MFCCs from reference clips.
+
+    Returns dict with:
+      - mean_vector: averaged MFCC across all clips (20,)
+      - clip_vectors: list of individual MFCC vectors
+    Returns None if no clips could be loaded.
+    """
+    vectors = []
+    for p in clip_paths:
+        try:
+            vec = _extract_mfcc(p)
+            vectors.append(vec)
+        except Exception as e:
+            _log(f"audio_scan: skip {p}: {e}")
+    if not vectors:
+        return None
+    arr = np.stack(vectors)
+    return {
+        "mean_vector": arr.mean(axis=0),
+        "clip_vectors": vectors,
+    }