Add scrolling mode for consolidation steps and fix tie handling

Integrate tie-aware step generation into practice session

Add tie support for MusicXML parsing, building, and practice steps

Add MIDI file upload support and UI improvements

Add MXL (compressed MusicXML) file support

Fix fingering toggle and progress bar, add system breaks

Add E2E tests for SVG timing verification of built-in songs

Add round-trip tests for MusicXML parsing and timing

Add built-in public domain songs for practice

Fix MusicXML parser to handle multiple voices with backup/forward

Add MusicXML upload with progressive practice mode

Fix duplicate note scheduling and clean up warnings

Fix README to accurately reflect level system and architecture

Update CLAUDE.md for new level system and modular architecture

Add modular architecture with reusable components