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- Replace Swift Array<UInt8> ring buffer with UnsafeMutableRawPointer to eliminate COW ref-count checks on every write/read - Add append(from:count:) to copy directly from Core Audio buffer pointer into the ring buffer, removing the per-callback Data heap allocation - Pre-allocate AVAudioPCMBuffer pair in AudioFormatConverter and reuse across transform() calls (lazy init, capacity-checked) - Fix float-to-int truncation in output frame count calculation (ceil) - Add comprehensive AudioBuffer test suite (12 tests) including proper wrap-around coverage for both append and read paths Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>