Hide approved automatic review warnings in the TUI (#39605)

## What changed

- Ignore Guardian warning notifications that report a successful automatic approval review, keeping approved reviews out of TUI history.
- Continue displaying all other Guardian warnings.
- Extend the approved-review history test to cover the notification path.

GitOrigin-RevId: 719e84bc5b20c0a5364d10f84be9c6ac96158719

codex-rs/tui/src/chatwidget/protocol.rs

@@ -154,7 +154,12 @@ impl ChatWidget {
             }
             ServerNotification::Warning(notification) => self.on_warning(notification.message),
             ServerNotification::GuardianWarning(notification) => {
-                self.on_warning(notification.message)
+                if !notification
+                    .message
+                    .starts_with("Automatic approval review approved (")
+                {
+                    self.on_warning(notification.message);
+                }
             }
             ServerNotification::DeprecationNotice(notification) => {
                 self.on_deprecation_notice(notification.summary, notification.details)