feat: reset memories button (#17937)

<img width="720" height="175" alt="Screenshot 2026-04-15 at 14 35 02"
src="https://github.com/user-attachments/assets/041d73ff-8c16-42a9-8e92-c245805084f0"
/>

codex-rs/tui/src/app_event.rs

@@ -470,6 +470,9 @@ pub(crate) enum AppEvent {
         generate_memories: bool,
     },
 
+    /// Clear all persisted local memory artifacts via the app-server.
+    ResetMemories,
+
     /// Update whether the full access warning prompt has been acknowledged.
     UpdateFullAccessWarningAcknowledged(bool),