docs(ios): drop stale debug comments + TeamTalk refs from audio router

After the stereo-mic/A2DP debugging settled, the iOS audio code carried
leftover TeamTalk5 comparison notes, source-line citations, TEMP DIAGNOSTIC
markers, and "this was the bug" narratives that no longer help. Reworded
those to state the current rules; kept the comments that document real
constraints (the setPreferredInputNumberOfChannels(2) trap, the re-entrancy
guard, the ma_context no-session-management config).

Comment-only — no behavior change. core builds, ctest --preset dev 21/21.

clients/apple/iOS/VoiceCatiOS/SessionState.swift

@@ -101,8 +101,7 @@ final class SessionState {
             addActivity(talking ? "\(who) started talking" : "\(who) stopped talking")
         case .streamStarted:
             // A remote user started a stream — ensure the audio session is active so we can
-            // hear them even if we haven't joined voice ourselves. Previously the session was
-            // only activated when the user pressed Join Voice, so remote audio was silent.
+            // hear them even if we haven't joined voice ourselves.
             if ev.userId != selfUserId {
                 do {
                     try AudioSessionManager.shared.ensureSessionActive()
@@ -110,8 +109,6 @@ final class SessionState {
                     addActivity("Audio session activate failed: \(error)")
                 }
             }
-            // TEMP DIAGNOSTIC: the core opens its miniaudio devices around now — log the
-            // session state to confirm miniaudio is no longer resetting the category to Record.
             AudioSessionManager.shared.logSessionState("stream started (user \(ev.userId))")
             addActivity("Stream started (user \(ev.userId))")
         case .streamStopped: