Replace Data/AudioPacket allocations with raw pointer callbacks through
the entire audio pipeline. Ring buffer hands out direct pointers (or
linearizes into a pre-allocated scratch buffer on wrap-around), converter
accepts/emits pointers via its cached buffers, and output handler writes
to stdout via write(2) with EINTR handling.
Remove AudioPacket (dead code), --flush flag (no-op with raw write(2)).
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Nick Payne