"""File Scanner module.

Responsibility: discover source audio files from the filesystem.

Capabilities (per SPEC.md §23.1):
- Recursive file discovery
- SHA-256 hashing (streamed)
- Duplicate detection
- Supported format filtering (wav, flac, aiff, aif)
- Output: TrackManifestCollection

This module must NOT decode audio, calculate features, access SQLite,
import SQLAlchemy, or write recommendations.
"""