agent: Increase message editor height (#28618)

It was too tiny, felt like we could use more breathing room.

Release Notes:

- N/A

crates/agent/src/message_editor.rs

@@ -56,7 +56,7 @@ pub struct MessageEditor {
     _subscriptions: Vec<Subscription>,
 }
 
-const MAX_EDITOR_LINES: usize = 10;
+const MAX_EDITOR_LINES: usize = 3;
 
 impl MessageEditor {
     pub fn new(
@@ -424,7 +424,11 @@ impl MessageEditor {
                     .when(is_editor_expanded, |this| {
                         this.h(vh(0.8, window)).justify_between()
                     })
-                    .child(div().when(is_editor_expanded, |this| this.h_full()).child({
+                    .child(
+                        div()
+                            .min_h_16()
+                            .when(is_editor_expanded, |this| this.h_full())
+                            .child({
                                 let settings = ThemeSettings::get_global(cx);
 
                                 let text_style = TextStyle {
@@ -448,7 +452,8 @@ impl MessageEditor {
                                     },
                                 )
                                 .into_any()
-                    }))
+                            }),
+                    )
                     .child(
                         h_flex()
                             .flex_none()