[stack 2/4] Align main realtime v2 wire and runtime flow (#14830)

## Stack Position
2/4. Built on top of #14828.

## Base
- #14828

## Unblocks
- #14829
- #14827

## Scope
- Port the realtime v2 wire parsing, session, app-server, and
conversation runtime behavior onto the split websocket-method base.
- Branch runtime behavior directly on the current realtime session kind
instead of parser-derived flow flags.
- Keep regression coverage in the existing e2e suites.

---------

Co-authored-by: Codex <noreply@openai.com>

codex-rs/tui_app_server/src/chatwidget/realtime.rs

@@ -268,9 +268,11 @@ impl ChatWidget {
             RealtimeEvent::SessionUpdated { session_id, .. } => {
                 self.realtime_conversation.session_id = Some(session_id);
             }
+            RealtimeEvent::InputAudioSpeechStarted(_) => self.interrupt_realtime_audio_playback(),
             RealtimeEvent::InputTranscriptDelta(_) => {}
             RealtimeEvent::OutputTranscriptDelta(_) => {}
             RealtimeEvent::AudioOut(frame) => self.enqueue_realtime_audio_out(&frame),
+            RealtimeEvent::ResponseCancelled(_) => self.interrupt_realtime_audio_playback(),
             RealtimeEvent::ConversationItemAdded(_item) => {}
             RealtimeEvent::ConversationItemDone { .. } => {}
             RealtimeEvent::HandoffRequested(_) => {}
@@ -313,6 +315,16 @@ impl ChatWidget {
         }
     }
 
+    #[cfg(not(target_os = "linux"))]
+    fn interrupt_realtime_audio_playback(&mut self) {
+        if let Some(player) = &self.realtime_conversation.audio_player {
+            player.clear();
+        }
+    }
+
+    #[cfg(target_os = "linux")]
+    fn interrupt_realtime_audio_playback(&mut self) {}
+
     #[cfg(not(target_os = "linux"))]
     fn start_realtime_local_audio(&mut self) {
         if self.realtime_conversation.capture_stop_flag.is_some() {

codex-rs/tui_app_server/src/voice.rs

@@ -426,6 +426,7 @@ fn send_realtime_audio_chunk(
             sample_rate: MODEL_AUDIO_SAMPLE_RATE,
             num_channels: MODEL_AUDIO_CHANNELS,
             samples_per_channel: Some(samples_per_channel),
+            item_id: None,
         },
     });
 }