Add Octatrack export command

[pixelate]

Summary

• Adds wavesync set export <name> --device <device> CLI subcommand
• Implements OctatrackExporter that generates a complete Octatrack DPS-1 project: project.work (text config), bank01–16.work (binary pattern banks), arr01–08.work (arrangements), and markers.work
• Reverse-engineered binary bank format from a reference project; bank files are generated from gzip-compressed templates (~3 KB total) with track assignments patched at known offsets and checksum recalculated
• Track 1 → static slot 1 (first song), Track 5 → static slot 2 (second song); all songs assigned to sequential static slots; FLEX recorder slots 129–136 included
• Project folder is named after the set in uppercase; prompts before overwriting an existing project
• Adds optional projects_path to device config in wavesync.yml, separate from path (audio sync destination)
• Calls sync after writing files to allow clean unmounting on macOS

Test plan

• rake — rubocop, steep, and all 278 tests pass
• Add projects_path to an Octatrack device entry in wavesync.yml
• Run wavesync set export <name> --device <device> and verify the generated project loads correctly on an Octatrack DPS-1