Add once_cell 1.21.4 and a Lazy‑initialized HashMap to store OGG bytes.
Replace file reads with in‑memory Cursor decoding, fix the
SoundrackParts enum typo, and derive Hash traits for it.
Introduce a `ChangePart` variant to `AudioCmd` and a `current_part`
state in
`handle_audio`. The audio sink is now created via
`DeviceSinkBuilder::from_default_device` with a fixed buffer size.
`load_audio`
now accepts a reference to `SoundrackParts`, and the player
automatically
queues the correct part when the queue becomes empty.