editor: Hide mouse context menu when modal is opened (#29127)

Closes #28787 

The context menu appears before the modal because it is a Deferred
element, which is always displayed above normal elements.

Release Notes:

Previously, the editor context menu appeared before the Command Palette.
This commit ensures the editor context menu is hidden when a modal,
including the Command Palette, is opened.

crates/workspace/src/modal_layer.rs

@@ -1,6 +1,6 @@
 use gpui::{
-    AnyView, DismissEvent, Entity, FocusHandle, Focusable as _, ManagedView, MouseButton,
-    Subscription,
+    AnyView, DismissEvent, Entity, EventEmitter, FocusHandle, Focusable as _, ManagedView,
+    MouseButton, Subscription,
 };
 use ui::prelude::*;
 
@@ -56,6 +56,10 @@ pub struct ModalLayer {
     dismiss_on_focus_lost: bool,
 }
 
+pub(crate) struct ModalOpenedEvent;
+
+impl EventEmitter<ModalOpenedEvent> for ModalLayer {}
+
 impl Default for ModalLayer {
     fn default() -> Self {
         Self::new()
@@ -84,6 +88,7 @@ impl ModalLayer {
         }
         let new_modal = cx.new(|cx| build_view(window, cx));
         self.show_modal(new_modal, window, cx);
+        cx.emit(ModalOpenedEvent);
     }
 
     fn show_modal<V>(&mut self, new_modal: Entity<V>, window: &mut Window, cx: &mut Context<Self>)

crates/workspace/src/workspace.rs

@@ -781,6 +781,7 @@ pub enum Event {
         language: &'static str,
     },
     ZoomChanged,
+    ModalOpened,
 }
 
 #[derive(Debug)]
@@ -1051,6 +1052,13 @@ impl Workspace {
         cx.emit(Event::WorkspaceCreated(weak_handle.clone()));
         let modal_layer = cx.new(|_| ModalLayer::new());
         let toast_layer = cx.new(|_| ToastLayer::new());
+        cx.subscribe(
+            &modal_layer,
+            |_, _, _: &modal_layer::ModalOpenedEvent, cx| {
+                cx.emit(Event::ModalOpened);
+            },
+        )
+        .detach();
 
         let bottom_dock_layout = WorkspaceSettings::get_global(cx).bottom_dock_layout;
         let left_dock = Dock::new(DockPosition::Left, modal_layer.clone(), window, cx);