fix(ui): keep a right-click in an open menu from opening the toolbar menu

Right-clicking an entry of the in-app main menu (Windows and Linux), such as a project under File › Open Recent, opened the title bar's toolbar menu (Project Widget, VCS Widget, …): the menu is rendered in a popup but is a child of the title bar in the component tree, so the contextmenu event reached the title bar's handler. A menu now consumes right-clicks itself, which covers every menu shown above another component's context menu.

src/ui/Menu.tsx

@@ -344,6 +344,9 @@ export function MenuList({
       aria-label={aria["aria-label"]}
       className={styles.menu}
       onKeyDown={onKeyDown}
+      // A right-click in an open menu does nothing; without this it reaches whatever is under the
+      // menu in the component tree, e.g. the title bar's toolbar menu behind File › Open Recent.
+      onContextMenu={(e) => e.preventDefault()}
       onPointerMove={(e) => {
         if (e.currentTarget.contains(e.target as Node)) pointerMove({ x: e.clientX, y: e.clientY });
       }}

src/ui/Popup.test.tsx

@@ -283,6 +283,17 @@ describe("Menu action enablement", () => {
     expect(open).toHaveFocus();
   });
 
+  it("keeps a right-click in a menu from reaching the components behind it", () => {
+    const behind = vi.fn((e: { defaultPrevented: boolean }) => e.defaultPrevented);
+    render(
+      <div onContextMenu={(e) => behind(e)}>
+        <MenuList items={[{ label: "Recent", run: () => undefined }]} onDone={() => {}} />
+      </div>,
+    );
+    fireEvent.contextMenu(screen.getByRole("menuitem", { name: "Recent" }));
+    expect(behind).toHaveReturnedWith(true);
+  });
+
   it("reports a hovered row once and lets the keyboard continue from it", () => {
     const active: string[] = [];
     const item = (label: string) => ({ label, onActive: () => active.push(label), run: () => undefined });