replace login screen with a simple prompt (#1713)

Perhaps there was an intention to make the login screen prettier, but it
feels quite silly right now to just have a screen that says "press q",
so replace it with something that lets the user directly login without
having to quit the app.

<img width="1283" height="635" alt="Screenshot 2025-07-28 at 2 54 05 PM"
src="https://github.com/user-attachments/assets/f19e5595-6ef9-4a2d-b409-aa61b30d3628"
/>

codex-rs/tui/src/main.rs

@@ -21,7 +21,7 @@ fn main() -> anyhow::Result<()> {
             .config_overrides
             .raw_overrides
             .splice(0..0, top_cli.config_overrides.raw_overrides);
-        let usage = run_main(inner, codex_linux_sandbox_exe)?;
+        let usage = run_main(inner, codex_linux_sandbox_exe).await?;
         println!("{}", codex_core::protocol::FinalOutput::from(usage));
         Ok(())
     })