- Rename milestone from 'Features & Extensibility' to 'Multi-Library Support'
- Replace old phases 10-14 (TAG/SMRT/GAP/MB/LAYOUT/PLUG) with 20 multi-library requirements (LIB/LSCAN/VIEW/PLAY/DATA)
- Move deferred features to Future Requirements
- Update research files with multi-library research (Stack, Features, Architecture, Pitfalls)
- Architecture: hybrid model (library_id on audio_files only), libraries in DB, sequential scanning, phantom tracks
yonlu