Only show Copy Code button on hover

crates/agent/src/active_thread.rs

@@ -439,6 +439,7 @@ fn render_markdown_code_block(
             .icon_color(Color::Muted)
             .shape(ui::IconButtonShape::Square)
             .tooltip(Tooltip::text("Copy Code"))
+            .visible_on_hover("markdown-code-block")
             .on_click({
                 let active_thread = active_thread.clone();
                 let parsed_markdown = parsed_markdown.clone();

crates/markdown/src/markdown.rs

@@ -861,7 +861,15 @@ impl Element for MarkdownElement {
                                     self.markdown.clone(),
                                     cx,
                                 );
-                                el.child(div().absolute().top_1().right_1().w_5().child(codeblock))
+                                el.child(
+                                    div()
+                                        .group("markdown-code-block")
+                                        .absolute()
+                                        .top_1()
+                                        .right_1()
+                                        .w_5()
+                                        .child(codeblock),
+                                )
                             });
                         }