Add realtime voice selection (#17176)

- Add realtime voice selection for realtime/start.
- Expose the supported v1/v2 voice lists and cover explicit, configured,
default, and invalid voice paths.

codex-rs/codex-api/src/endpoint/realtime_websocket/methods_v1.rs

@@ -7,11 +7,11 @@ use crate::endpoint::realtime_websocket::protocol::ConversationItemType;
 use crate::endpoint::realtime_websocket::protocol::ConversationMessageItem;
 use crate::endpoint::realtime_websocket::protocol::ConversationRole;
 use crate::endpoint::realtime_websocket::protocol::RealtimeOutboundMessage;
+use crate::endpoint::realtime_websocket::protocol::RealtimeVoice;
 use crate::endpoint::realtime_websocket::protocol::SessionAudio;
 use crate::endpoint::realtime_websocket::protocol::SessionAudioFormat;
 use crate::endpoint::realtime_websocket::protocol::SessionAudioInput;
 use crate::endpoint::realtime_websocket::protocol::SessionAudioOutput;
-use crate::endpoint::realtime_websocket::protocol::SessionAudioVoice;
 use crate::endpoint::realtime_websocket::protocol::SessionType;
 use crate::endpoint::realtime_websocket::protocol::SessionUpdateSession;
 
@@ -38,7 +38,10 @@ pub(super) fn conversation_handoff_append_message(
     }
 }
 
-pub(super) fn session_update_session(instructions: String) -> SessionUpdateSession {
+pub(super) fn session_update_session(
+    instructions: String,
+    voice: RealtimeVoice,
+) -> SessionUpdateSession {
     SessionUpdateSession {
         id: None,
         r#type: SessionType::Quicksilver,
@@ -56,7 +59,7 @@ pub(super) fn session_update_session(instructions: String) -> SessionUpdateSessi
             },
             output: Some(SessionAudioOutput {
                 format: None,
-                voice: SessionAudioVoice::Fathom,
+                voice,
             }),
         },
         tools: None,