refactor(ws-utils): remove unused Phase 3 abstractions

Remove AudioSamples, SampleBuffer, SampleSource, and BufferedAudioStream
as they were not integrated with existing code. The deduplication of
WebSocketAudioSource and ChannelAudioSource can be done in a follow-up PR.

Co-Authored-By: yujonglee <yujonglee.dev@gmail.com>

Author: devin-ai-integration[bot]

crates/ws-utils/src/audio.rs

@@ -1,14 +1,10 @@
 //! Utilities for WebSocket-based audio streaming.
 //!
-//! This crate provides shared abstractions for audio buffering, sample sources,
-//! and connection management used by WebSocket audio clients.
+//! This crate provides connection management and audio source abstractions
+//! for WebSocket-based audio clients.
 
-mod audio;
-mod buffered_stream;
 mod manager;
 
-pub use audio::AudioSamples;
-pub use buffered_stream::{BufferedAudioStream, SampleBuffer, SampleSource};
 pub use manager::*;
 
 use std::pin::Pin;