Complete managed macOS platform bring-up

core/include/voicecat.h

@@ -453,7 +453,9 @@ VC_API vc_result vc_stream_feed_pcm(vc_client* c, uint32_t stream_id,
  * channels            : 1 or 2, matching the sender's stream configuration.
  * sample_rate         : always 48000 in the current implementation.
  *
- * Pass cb = NULL to disable (default: disabled; hardware playback only).
+ * Pass cb = NULL to disable (default: disabled; hardware playback only). Disabling is a
+ * quiescence barrier: when vc_set_pcm_sink(c, NULL, NULL) returns, no callback using the old
+ * user pointer is still running, so the caller may safely release that state.
  * The callback MUST NOT block, lock, or allocate — copy what you need and return.
  * PCM is still delivered to the hardware playback device regardless (dual output). */
 typedef void (*vc_pcm_sink_cb)(void* user, uint32_t user_id, uint32_t stream_id,
@@ -483,7 +485,8 @@ VC_API vc_result vc_set_pcm_sink(vc_client* c, vc_pcm_sink_cb cb, void* user);
  * steadily even with no remote streams (a silent block), so the renderer has a continuous
  * clock. The callback MUST NOT block, lock, or allocate — copy into a lock-free ring and
  * return. Independent of vc_set_pcm_sink (the per-stream tap), which still works. Pass cb=NULL
- * to disable (default: disabled). */
+ * to disable (default: disabled). Disabling is a quiescence barrier with the same callback-state
+ * lifetime guarantee as vc_set_pcm_sink. */
 typedef void (*vc_mixed_output_cb)(void* user, const int16_t* pcm,
                                    size_t samples_per_channel, uint32_t channels,
                                    uint32_t sample_rate);