assistant2: Add stray visual adjusments (#22386)

This PR adds just some tiny visual clean ups to the assistant2 panel.
Nothing major, honestly.

<img width="800" alt="Screenshot 2024-12-24 at 12 19 46 AM"
src="https://github.com/user-attachments/assets/da22aa7f-8a42-4ff0-9e4c-5e8b60b28802"
/>

Release Notes:

- N/A

crates/markdown/src/markdown.rs

@@ -614,11 +614,11 @@ impl Element for MarkdownElement {
                             };
                             builder.push_div(
                                 div()
+                                    .mb_1()
                                     .h_flex()
-                                    .mb_2()
-                                    .line_height(rems(1.3))
                                     .items_start()
                                     .gap_1()
+                                    .line_height(rems(1.3))
                                     .child(bullet),
                                 range,
                                 markdown_end,