quabynahdavis/soundkit-rust ? reverse-engineered prompt

Build me a Rust music theory toolkit called SoundKit.

I want it to work both as a command line app and as a reusable library. It should let me convert between note names, MIDI numbers, and frequencies, generate chords and scales, validate inputs like note names and octaves, and do a few useful conversion helpers like cents and ratios.

The CLI should feel simple and friendly, with commands for note conversion, chord building, scale building, validation, batch lookup, listing available chord and scale types, and a demo command that shows everything working. It should support common chord types and scale types, including inversions and multiple octaves.

For the library, expose clean functions that make it easy to use from another Rust project without a lot of setup. Keep the code organized and well tested, and make sure the output is accurate for common music theory cases.

If you need to check anything about current Rust docs or best practices, look it up online.