debugger: Remember focused item (#30722)

Release Notes:

- Debugger Beta: the `debug panel: toggle focus` action now preserves
the debug panel's focused item.

crates/debugger_ui/src/session/running.rs

@@ -81,6 +81,10 @@ impl RunningState {
     pub(crate) fn thread_id(&self) -> Option<ThreadId> {
         self.thread_id
     }
+
+    pub(crate) fn active_pane(&self) -> Option<&Entity<Pane>> {
+        self.active_pane.as_ref()
+    }
 }
 
 impl Render for RunningState {
@@ -502,20 +506,15 @@ impl DebugTerminal {
 
 impl gpui::Render for DebugTerminal {
     fn render(&mut self, _window: &mut Window, _: &mut Context<Self>) -> impl IntoElement {
-        if let Some(terminal) = self.terminal.clone() {
-            terminal.into_any_element()
-        } else {
-            div().track_focus(&self.focus_handle).into_any_element()
-        }
+        div()
+            .size_full()
+            .track_focus(&self.focus_handle)
+            .children(self.terminal.clone())
     }
 }
 impl Focusable for DebugTerminal {
-    fn focus_handle(&self, cx: &App) -> FocusHandle {
-        if let Some(terminal) = self.terminal.as_ref() {
-            return terminal.focus_handle(cx);
-        } else {
-            self.focus_handle.clone()
-        }
+    fn focus_handle(&self, _cx: &App) -> FocusHandle {
+        self.focus_handle.clone()
     }
 }