Make migration screen dynamic (#7896)

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codex-rs/tui/src/app_event.rs

@@ -139,7 +139,8 @@ pub(crate) enum AppEvent {
 
     /// Persist the acknowledgement flag for the model migration prompt.
     PersistModelMigrationPromptAcknowledged {
-        migration_config: String,
+        from_model: String,
+        to_model: String,
     },
 
     /// Skip the next world-writable scan (one-shot) after a user-confirmed continue.