whitelist command prefix integration in core and tui (#7033)

this PR enables TUI to approve commands and add their prefixes to an
allowlist:
<img width="708" height="605" alt="Screenshot 2025-11-21 at 4 18 07 PM"
src="https://github.com/user-attachments/assets/56a19893-4553-4770-a881-becf79eeda32"
/>

note: we only show the option to whitelist the command when 
1) command is not multi-part (e.g `git add -A && git commit -m 'hello
world'`)
2) command is not already matched by an existing rule

codex-rs/core/src/codex_delegate.rs

@@ -281,6 +281,7 @@ async fn handle_exec_approval(
         event.cwd,
         event.reason,
         event.risk,
+        event.allow_prefix,
     );
     let decision = await_approval_with_cancel(
         approval_fut,