agent: Fix agent panel model selector layout pushing send button off screen (#32251)

| Before | After |
|--------|-------|
| <video
src="https://github.com/user-attachments/assets/db4dcc91-9a32-4621-be78-87fe9d80b801"
controls width="400"></video> | <video
src="https://github.com/user-attachments/assets/8ee31d6d-5150-4239-a4af-eeca112d56d5"
controls width="400"></video> |

While working on something else I found this weird behaviour in message
editor of agent panel. When model names are too long, the model selector
would expand and push the send button outside the visible area. This
change fixes the flex layout to ensure the send button always remains
accessible while properly truncating long model names.

Closes #ISSUE

Release Notes:

- Fix agent panel model selector layout pushing send button off screen

---------

Co-authored-by: Danilo Leal <daniloleal09@gmail.com>
Co-authored-by: Danilo Leal <67129314+danilo-leal@users.noreply.github.com>

crates/agent/src/agent_model_selector.rs

@@ -91,12 +91,13 @@ impl AgentModelSelector {
 
 impl Render for AgentModelSelector {
     fn render(&mut self, window: &mut Window, cx: &mut Context<Self>) -> impl IntoElement {
-        let focus_handle = self.focus_handle.clone();
-
         let model = self.selector.read(cx).delegate.active_model(cx);
         let model_name = model
             .map(|model| model.model.name().0)
             .unwrap_or_else(|| SharedString::from("No model selected"));
+
+        let focus_handle = self.focus_handle.clone();
+
         PickerPopoverMenu::new(
             self.selector.clone(),
             Button::new("active-model", model_name)

crates/agent/src/message_editor.rs

@@ -722,6 +722,7 @@ impl MessageEditor {
                     .child(
                         h_flex()
                             .flex_none()
+                            .flex_wrap()
                             .justify_between()
                             .child(
                                 h_flex()
@@ -731,6 +732,7 @@ impl MessageEditor {
                             .child(
                                 h_flex()
                                     .gap_1()
+                                    .flex_wrap()
                                     .when(!incompatible_tools.is_empty(), |this| {
                                         this.child(
                                             IconButton::new(