agent_ui: Ensure that all configuration views get rendered with full width (#36362)

Closes #36097

Release Notes:

- Fixed API key input fields getting shrunk in Agent Panel settings view
on low panel widths paired with high UI font sizes.

crates/agent_ui/src/agent_configuration.rs

@@ -300,6 +300,7 @@ impl AgentConfiguration {
             )
             .child(
                 div()
+                    .w_full()
                     .px_2()
                     .when(is_expanded, |parent| match configuration_view {
                         Some(configuration_view) => parent.child(configuration_view),