agent: Add UI for upsell scenarios (#29805)

Release Notes:

- N/A

---------

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

crates/ui/src/components.rs

@@ -1,6 +1,7 @@
 mod avatar;
 mod banner;
 mod button;
+mod callout;
 mod content_group;
 mod context_menu;
 mod disclosure;
@@ -41,6 +42,7 @@ mod stories;
 pub use avatar::*;
 pub use banner::*;
 pub use button::*;
+pub use callout::*;
 pub use content_group::*;
 pub use context_menu::*;
 pub use disclosure::*;