agent: Add UI for upsell scenarios (#29805)

Release Notes:

- N/A

---------

Co-authored-by: Marshall Bowers <git@maxdeviant.com>

crates/agent/src/ui.rs

@@ -1,14 +1,12 @@
 mod agent_notification;
-pub mod agent_preview;
 mod animated_label;
 mod context_pill;
 mod max_mode_tooltip;
+pub mod preview;
 mod upsell;
 mod usage_banner;
 
 pub use agent_notification::*;
-pub use agent_preview::*;
 pub use animated_label::*;
 pub use context_pill::*;
 pub use max_mode_tooltip::*;
-pub use usage_banner::*;