Remove lead/worker provider (#7989)

Signed-off-by: Douwe Osinga <douwe@squareup.com>
Co-authored-by: Douwe Osinga <douwe@squareup.com>

crates/goose-server/src/routes/reply.rs

@@ -137,10 +137,6 @@ pub enum MessageEvent {
         reason: String,
         token_state: TokenState,
     },
-    ModelChange {
-        model: String,
-        mode: String,
-    },
     Notification {
         request_id: String,
         #[schema(value_type = Object)]
@@ -364,9 +360,6 @@ pub async fn reply(
                             stream_event(MessageEvent::UpdateConversation {conversation: new_messages}, &tx, &cancel_token).await;
 
                         }
-                        Ok(Some(Ok(AgentEvent::ModelChange { model, mode }))) => {
-                            stream_event(MessageEvent::ModelChange { model, mode }, &tx, &cancel_token).await;
-                        }
                         Ok(Some(Ok(AgentEvent::McpNotification((request_id, n))))) => {
                             stream_event(MessageEvent::Notification{
                                 request_id: request_id.clone(),

crates/goose-server/src/routes/session_events.rs

@@ -462,13 +462,6 @@ pub async fn session_reply(
                             )
                             .await;
                         }
-                        Ok(Some(Ok(AgentEvent::ModelChange { model, mode }))) => {
-                            publish(
-                                Some(task_request_id.clone()),
-                                MessageEvent::ModelChange { model, mode },
-                            )
-                            .await;
-                        }
                         Ok(Some(Ok(AgentEvent::McpNotification((notification_request_id, n))))) => {
                             publish(
                                 Some(task_request_id.clone()),