Stability and cleanup update

Wow, how time flies!

Music-generation improvements

MuGen is now smarter

• Improved melody and chord alignment, especially for chord-based and strummed melodies.
• Fixed pentatonic, blues, modal, chorus, bridge, and solo sections so they respect the selected key and scale more consistently.
• Improved modal progressions, cadences, random key selection, and seventh/sus/add chord behavior.
• Fixed rhythm and timing issues that could cause unexpected rests, muted sections, drifting drums/bass, or invalid very short notes.
• Fixed randomized instruments and drums sometimes choosing the wrong sounds.
• Improved seed reproducibility, batch generation, exported track naming, and metadata output.
• Fixed several UI, playback, settings, startup, and command line crashes.