Wire realtime api to core (#12268)

- Introduce `RealtimeConversationManager` for realtime API management 
- Add `op::conversation` to start conversation, insert audio, insert
text, and close conversation.
- emit conversation lifecycle and realtime events.
- Move shared realtime payload types into codex-protocol and add core
e2e websocket tests for start/replace/transport-close paths.

Things to consider:
- Should we use the same `op::` and `Events` channel to carry audio? I
think we should try this simple approach and later we can create
separate one if the channels got congested.
- Sending text updates to the client: we can start simple and later
restrict that.
- Provider auth isn't wired for now intentionally

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

@@ -372,7 +372,8 @@ impl RealtimeWebsocketClient {
         default_headers: HeaderMap,
     ) -> Result<RealtimeWebsocketConnection, ApiError> {
         ensure_rustls_crypto_provider();
-        let ws_url = websocket_url_from_api_url(config.api_url.as_str())?;
+        // Keep provider base_url semantics aligned with HTTP clients; derive the ws endpoint here.
+        let ws_url = websocket_url_from_api_url(self.provider.base_url.as_str())?;
 
         let mut request = ws_url
             .as_str()
@@ -638,7 +639,7 @@ mod tests {
 
         let provider = Provider {
             name: "test".to_string(),
-            base_url: "http://localhost".to_string(),
+            base_url: format!("http://{addr}"),
             query_params: Some(HashMap::new()),
             headers: HeaderMap::new(),
             retry: crate::provider::RetryConfig {
@@ -654,7 +655,6 @@ mod tests {
         let connection = client
             .connect(
                 RealtimeSessionConfig {
-                    api_url: format!("ws://{addr}"),
                     prompt: "backend prompt".to_string(),
                     session_id: Some("conv_1".to_string()),
                 },
@@ -765,7 +765,7 @@ mod tests {
 
         let provider = Provider {
             name: "test".to_string(),
-            base_url: "http://localhost".to_string(),
+            base_url: format!("http://{addr}"),
             query_params: Some(HashMap::new()),
             headers: HeaderMap::new(),
             retry: crate::provider::RetryConfig {
@@ -781,7 +781,6 @@ mod tests {
         let connection = client
             .connect(
                 RealtimeSessionConfig {
-                    api_url: format!("ws://{addr}"),
                     prompt: "backend prompt".to_string(),
                     session_id: Some("conv_1".to_string()),
                 },

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

@@ -1,10 +1,10 @@
 pub mod methods;
 pub mod protocol;
 
+pub use codex_protocol::protocol::RealtimeAudioFrame;
+pub use codex_protocol::protocol::RealtimeEvent;
 pub use methods::RealtimeWebsocketClient;
 pub use methods::RealtimeWebsocketConnection;
 pub use methods::RealtimeWebsocketEvents;
 pub use methods::RealtimeWebsocketWriter;
-pub use protocol::RealtimeAudioFrame;
-pub use protocol::RealtimeEvent;
 pub use protocol::RealtimeSessionConfig;

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

@@ -1,33 +1,15 @@
-use serde::Deserialize;
+pub use codex_protocol::protocol::RealtimeAudioFrame;
+pub use codex_protocol::protocol::RealtimeEvent;
 use serde::Serialize;
 use serde_json::Value;
 use tracing::debug;
 
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct RealtimeSessionConfig {
-    pub api_url: String,
     pub prompt: String,
     pub session_id: Option<String>,
 }
 
-#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
-pub struct RealtimeAudioFrame {
-    pub data: String,
-    pub sample_rate: u32,
-    pub num_channels: u16,
-    #[serde(skip_serializing_if = "Option::is_none")]
-    pub samples_per_channel: Option<u32>,
-}
-
-#[derive(Debug, Clone, PartialEq, Eq)]
-pub enum RealtimeEvent {
-    SessionCreated { session_id: String },
-    SessionUpdated { backend_prompt: Option<String> },
-    AudioOut(RealtimeAudioFrame),
-    ConversationItemAdded(Value),
-    Error(String),
-}
-
 #[derive(Debug, Clone, Serialize)]
 #[serde(tag = "type")]
 pub(super) enum RealtimeOutboundMessage {

codex-rs/codex-api/src/lib.rs

@@ -29,8 +29,6 @@ pub use crate::endpoint::aggregate::AggregateStreamExt;
 pub use crate::endpoint::compact::CompactClient;
 pub use crate::endpoint::memories::MemoriesClient;
 pub use crate::endpoint::models::ModelsClient;
-pub use crate::endpoint::realtime_websocket::RealtimeAudioFrame;
-pub use crate::endpoint::realtime_websocket::RealtimeEvent;
 pub use crate::endpoint::realtime_websocket::RealtimeSessionConfig;
 pub use crate::endpoint::realtime_websocket::RealtimeWebsocketClient;
 pub use crate::endpoint::realtime_websocket::RealtimeWebsocketConnection;
@@ -44,3 +42,5 @@ pub use crate::provider::is_azure_responses_wire_base_url;
 pub use crate::sse::stream_from_fixture;
 pub use crate::telemetry::SseTelemetry;
 pub use crate::telemetry::WebsocketTelemetry;
+pub use codex_protocol::protocol::RealtimeAudioFrame;
+pub use codex_protocol::protocol::RealtimeEvent;