feat: add a macOS menu bar toggle for desktop

Adds a General settings switch to show or hide the macOS menu bar item.
Persists the new desktopMacMenuBarEnabled setting and passes tray state into Electron.
Disables tray sync and native tray setup when the menu bar is turned off.

packages/web/server/lib/opencode/settings-helpers.test.js

@@ -124,6 +124,20 @@ describe('settings helpers', () => {
     });
   });
 
+  it('accepts desktopMacMenuBarEnabled as a persisted shared setting', () => {
+    const helpers = createTestHelpers();
+
+    expect(helpers.sanitizeSettingsUpdate({ desktopMacMenuBarEnabled: true })).toEqual({
+      desktopMacMenuBarEnabled: true,
+    });
+    expect(helpers.sanitizeSettingsUpdate({ desktopMacMenuBarEnabled: false })).toEqual({
+      desktopMacMenuBarEnabled: false,
+    });
+    expect(helpers.formatSettingsResponse({ desktopMacMenuBarEnabled: false })).toMatchObject({
+      desktopMacMenuBarEnabled: false,
+    });
+  });
+
   it('sanitizes the persisted permission auto-accept policy', () => {
     const helpers = createTestHelpers();