fix: Prevent /review crash when entering Esc on steer message (#22879)

This changes the `/review` escape path so `Esc` no longer behaves like
the normal queued-follow-up interrupt flow while a review is running.
Steering is not currently supported in `/review` mode, without this
change users are able to attempt a steer but it leads to a crash (see
#22815). If the user has already tried to send additional guidance
during `/review`, the TUI now keeps the review running and shows a
warning that steer messages are not supported in that mode, while still
pointing users to `Ctrl+C` if they actually want to cancel. It also adds
regression coverage for the review-specific warning behavior. When users
do cancel with Ctrl+C during /review, the TUI now tolerates the
active-turn race that can happen during review handoff, and any queued
steer messages are restored to the composer instead of being discarded.

- Special-case `Esc` during an active `/review` when follow-up steer
input is pending or has already been deferred.
- Show a clear warning instead of interrupting the running review.
- Make the Ctrl+C cancel path during /review resilient to active-turn
races, while preserving any queued steer text by restoring it to the
composer.
- Add review-mode test coverage for the warning path.

## Testing

1. Start a `/review` with a diff large enough that the review stays
active for more than a few seconds.

2. While the review is still running, type a follow-up / steer message,
submit it, and then press `Esc`.
   Before: `Esc` causes the TUI to close abruptly.  
After: the review keeps running and the transcript shows a warning that
steer messages are not supported during `/review`, with guidance to use
`Ctrl+C` if you want to cancel.

3. Press `Ctrl+C` if you actually want to stop the review.  
Before: (after restarting the test since Pt. 2 crashed) this is the
intentional cancellation path.
After: this remains the intentional cancellation path, and any queued
follow-up steer text is restored to the composer instead of being lost.
   
## Note:
`/review` mode explicitly does not support steering at this time (as
noted in `turn_processer.rs`, if we want to explore that in the future
this code will need to be modified). This change keeps unsupported steer
attempts from crashing the TUI and preserves queued follow-up text if
the user cancels with Ctrl+C.

codex-rs/tui/src/app_server_session.rs

@@ -736,7 +736,7 @@ impl AppServerSession {
         &mut self,
         thread_id: ThreadId,
         turn_id: String,
-    ) -> Result<()> {
+    ) -> std::result::Result<(), TypedRequestError> {
         let request_id = self.next_request_id();
         let _: TurnInterruptResponse = self
             .client
@@ -747,12 +747,14 @@ impl AppServerSession {
                     turn_id,
                 },
             })
-            .await
-            .wrap_err("turn/interrupt failed in TUI")?;
+            .await?;
         Ok(())
     }
 
-    pub(crate) async fn startup_interrupt(&mut self, thread_id: ThreadId) -> Result<()> {
+    pub(crate) async fn startup_interrupt(
+        &mut self,
+        thread_id: ThreadId,
+    ) -> std::result::Result<(), TypedRequestError> {
         self.turn_interrupt(thread_id, String::new()).await
     }