git_ui: Prevent button overflow due to long names (#25940)

- Fix component preview widths for git panel
- Fix buttons getting pushed off the screen in git  panel

Release Notes:

- N/A

---------

Co-authored-by: Mikayla Maki <mikayla.c.maki@gmail.com>

crates/assistant2/src/assistant_panel.rs

@@ -609,7 +609,7 @@ impl AssistantPanel {
                     .id("title")
                     .overflow_x_scroll()
                     .px(DynamicSpacing::Base08.rems(cx))
-                    .child(Label::new(title).text_ellipsis()),
+                    .child(Label::new(title).truncate()),
             )
             .child(
                 h_flex()

crates/assistant2/src/thread_history.rs

@@ -260,7 +260,7 @@ impl RenderOnce for PastThread {
             .start_slot(
                 div()
                     .max_w_4_5()
-                    .child(Label::new(summary).size(LabelSize::Small).text_ellipsis()),
+                    .child(Label::new(summary).size(LabelSize::Small).truncate()),
             )
             .end_slot(
                 h_flex()
@@ -356,7 +356,7 @@ impl RenderOnce for PastContext {
         .start_slot(
             div()
                 .max_w_4_5()
-                .child(Label::new(summary).size(LabelSize::Small).text_ellipsis()),
+                .child(Label::new(summary).size(LabelSize::Small).truncate()),
         )
         .end_slot(
             h_flex()