fix(alsa): drop PCM IO before underrun recovery

[gulbrand]

I was testing my DAW on linux now that cpal has duplex for alsa. Ran into a few buffer underruns and my audio engine crapped out. Found a panic in the callback thread:

=== ENGINE PANIC (pid 414610) ===
panicked at /home/gulbrand/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/alsa-0.12.1/src/pcm.rs:149:27:
No hw_params call or additional IO objects allowed
Backtrace:
   ...
   6: <alsa::pcm::PCM>::io_bytes
   7: cpal::host::alsa::duplex::begin_duplex_playback
   8: cpal::host::alsa::duplex::duplex_stream_worker
   ...

I then used an ai agent to help me dig into this, as the error message wasn't quite helpful. It looks like it is a double borrow checked at runtime, and a solution is to let go of the borrow before entering the match arms so that calling recover_duplex isn't called while already holding the borrow on the io object.

It only hits on the match arms that call recover_duplex, so only in error conditions as far as I can tell.

I've confirmed that an underrun no longer panics -- I'm using Omarchy Quattro as my lab test.