docs: condense implementation comments

clients/apple/Sources/VoiceCatCore/Callbacks.swift

@@ -1,19 +1,5 @@
-// Callbacks — the C function pointers passed to `vc_callbacks`. These are the Swift
-// equivalent of the C# client's `[UnmanagedCallersOnly]` static methods (NativeCallbacks.cs).
-//
-// The critical patterns (carried over from the proven C# implementation):
-//   1. `@convention(c)` closures — plain C function pointers, NOT GC/ARC-managed closures.
-//      A @convention(c) closure cannot capture context, which is why the `user` pointer is
-//      used to resolve back to the VoiceCatClient instance (the C# version uses GCHandle for
-//      the same thing; Swift uses Unmanaged).
-//   2. `Unmanaged.passUnretained(self).toOpaque()` as the `user` context — a stable raw
-//      pointer to the Swift object WITHOUT incrementing the retain count. This is safe
-//      because `deinit` calls `vc_client_destroy` (which synchronously joins every internal
-//      thread) BEFORE the object's memory is freed — so no callback can fire after the object
-//      is gone. (The C# equivalent: GCHandle.Alloc + GCHandle.Free in Dispose.)
-//   3. Copy `ev.text` to a Swift `String` INSIDE `onEvent` (via `VoiceCatEvent.from(_:)`)
-//      before returning — the raw pointer is dangling after the callback returns. This is
-//      the #1 lifetime rule from voicecat.h's vc_event doc comment.
+// C callbacks use an unretained `user` context. Client destruction joins callback threads,
+// and transient event pointers are copied before the callback returns.
 
 import VoiceCatC
 import Foundation