feat: TUI undo op (#5629)

codex-rs/protocol/src/protocol.rs

@@ -178,6 +178,9 @@ pub enum Op {
     /// to generate a summary which will be returned as an AgentMessage event.
     Compact,
 
+    /// Request Codex to undo a turn (turn are stacked so it is the same effect as CMD + Z).
+    Undo,
+
     /// Request a code review from the agent.
     Review { review_request: ReviewRequest },
 
@@ -486,6 +489,10 @@ pub enum EventMsg {
 
     BackgroundEvent(BackgroundEventEvent),
 
+    UndoStarted(UndoStartedEvent),
+
+    UndoCompleted(UndoCompletedEvent),
+
     /// Notification that a model stream experienced an error or disconnect
     /// and the system is handling it (e.g., retrying with backoff).
     StreamError(StreamErrorEvent),
@@ -1135,6 +1142,19 @@ pub struct BackgroundEventEvent {
     pub message: String,
 }
 
+#[derive(Debug, Clone, Deserialize, Serialize, JsonSchema, TS)]
+pub struct UndoStartedEvent {
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub message: Option<String>,
+}
+
+#[derive(Debug, Clone, Deserialize, Serialize, JsonSchema, TS)]
+pub struct UndoCompletedEvent {
+    pub success: bool,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub message: Option<String>,
+}
+
 #[derive(Debug, Clone, Deserialize, Serialize, JsonSchema, TS)]
 pub struct StreamErrorEvent {
     pub message: String,