feat: replace native title bar with custom TitleBar and integrate tab bar

This commit removes the native OS title bar and introduces a cross-platform custom title bar using gpui-component's TitleBar. To optimize vertical screen space, the tab bar has been relocated into the newly created custom title bar.

Fixes #37

src/app/startup.rs

@@ -176,7 +176,10 @@ pub(crate) fn sync_macos_launch_environment() {
 pub(crate) fn sync_macos_launch_environment() {}
 
 pub(crate) fn open_main_window(cx: &mut App) {
-    let mut window_options = WindowOptions::default();
+    let mut window_options = WindowOptions {
+        titlebar: Some(gpui_component::TitleBar::title_bar_options()),
+        ..Default::default()
+    };
 
     #[cfg(not(target_os = "macos"))]
     if let Ok(img) = image::load_from_memory(include_bytes!("../../assets/icons/ashell.png")) {

src/app/ui.rs

@@ -2431,7 +2431,6 @@ impl Render for Ashell {
                                 .size_full()
                                 .relative()
                                 .overflow_hidden()
-                                .child(self.render_tab_bar(cx))
                                 .child(body_panel),
                         ),
                 )
@@ -2452,7 +2451,6 @@ impl Render for Ashell {
                     .size_full()
                     .relative()
                     .overflow_hidden()
-                    .child(self.render_tab_bar(cx))
                     .child(body_panel),
             );
 
@@ -2463,7 +2461,7 @@ impl Render for Ashell {
                 .into_any_element()
         };
 
-        div()
+        v_flex()
             .id("ashell-root")
             .size_full()
             .bg(cx.theme().background)
@@ -2495,7 +2493,14 @@ impl Render for Ashell {
                     this.close_tab(active_id, cx);
                 }
             }))
-            .child(workspace)
+            .child(
+                gpui_component::TitleBar::new().child(
+                    div().flex().items_center().w_full().child(self.render_tab_bar(cx)),
+                ),
+            )
+            .child(
+                div().flex_1().min_h_0().child(workspace),
+            )
             .children(Root::render_dialog_layer(window, cx))
             .children(Root::render_sheet_layer(window, cx))
             .when_some(self.sftp_context_menu.clone(), |this, menu| {