Fix editor & assistant panel toolbar height mismatch (#15552)

This PR ensures that the toolbar within the editor and the assistant
panel have the same height. I also pushed in some other tiny design
(spacing, really) tweaks. There's still a mismatch between the editor
toolbar and the assistant panel's history tab, but I'll try to tackle
this separately.

---

Release Notes:

- N/A

crates/search/src/buffer_search.rs

@@ -196,6 +196,7 @@ impl Render for BufferSearchBar {
         };
 
         let search_line = h_flex()
+            .mb_1()
             .child(
                 h_flex()
                     .id("editor-scroll")
@@ -295,7 +296,7 @@ impl Render for BufferSearchBar {
                         &SelectNextMatch,
                     ))
                     .when(!narrow_mode, |this| {
-                        this.child(h_flex().min_w(rems_from_px(40.)).child(
+                        this.child(h_flex().ml_2().min_w(rems_from_px(40.)).child(
                             Label::new(match_text).color(if self.active_match_index.is_some() {
                                 Color::Default
                             } else {

crates/workspace/src/toolbar.rs

@@ -105,6 +105,7 @@ impl Render for Toolbar {
             .bg(cx.theme().colors().toolbar_background)
             .child(
                 h_flex()
+                    .min_h(rems_from_px(24.))
                     .justify_between()
                     .gap(Spacing::Large.rems(cx))
                     .when(has_left_items, |this| {