Sync rollback model-visible mode state across core and tui

codex-rs/protocol/src/protocol.rs

@@ -1979,6 +1979,18 @@ pub struct UndoCompletedEvent {
 pub struct ThreadRolledBackEvent {
     /// Number of user turns that were removed from context.
     pub num_turns: u32,
+    /// Model-visible session state after rollback.
+    ///
+    /// This lets clients synchronize UI mode/model indicators with core after history rewind.
+    /// Optional for backward compatibility with older persisted events.
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub model_visible_state: Option<ModelVisibleState>,
+}
+
+#[derive(Debug, Clone, Deserialize, Serialize, PartialEq, Eq, JsonSchema, TS)]
+pub struct ModelVisibleState {
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub collaboration_mode: Option<CollaborationMode>,
 }
 
 #[derive(Debug, Clone, Deserialize, Serialize, JsonSchema, TS)]