The Windows build of pf-client-core has been red on main since the
pad-audio merge (#23): pad_audio.rs calls
`crate::audio_wasapi::device_by_id`, but lib.rs mounts audio_wasapi.rs AS
`crate::audio` via the #[path] per-OS swap — the `audio_wasapi` module
name never exists. Windows-gated call site, so every Linux leg stayed
green while both `windows / build` targets failed E0433.
One-line rename to the mounted path (+ the comment that pointed readers
at the phantom name). Verification is the PR's own windows leg — the
crate builds on no other platform this path compiles on.
enricobuehler