feat: add system theme toggle command

Tests/ConjureKitTests/ShortcutDestinationTests.swift

@@ -33,7 +33,7 @@ import Testing
     #expect(search.accessibilityLabel() == "Search applications, calculate, or convert units and currencies")
 }
 
-@Test(arguments: Application.Command.allCases, [true, false])
+@Test(arguments: [Application.Command.translate, .emoji, .notes], [true, false])
 @MainActor func commandsAreFullyVisibleImmediately(_ command: Application.Command, _ fromShortcut: Bool) throws {
     _ = NSApplication.shared
     let suite = "ConjurePresentation.\(UUID().uuidString)"
@@ -65,6 +65,7 @@ import Testing
             case .emoji: $0 is NSCollectionView
             case .translate: $0.accessibilityLabel() == "Japanese translation"
             case .notes: $0.accessibilityLabel() == "Note editor"
+            case .toggleTheme: false
             }
         }
     })