fix: resolve macos bun interop

Use Bun-safe Electron and child_process import patterns for macOS GitHub Actions tests.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

src/main/windows/titleBarTheme.ts

@@ -1,7 +1,10 @@
-import { nativeTheme, type BrowserWindow } from 'electron';
+import electron from 'electron';
+import type { BrowserWindow } from 'electron';
 
 import type { AppearanceTheme } from '@shared/domain/tooling';
 
+const { nativeTheme } = electron;
+
 interface TitleBarColors {
   backgroundColor: string;
   overlay: { color: string; symbolColor: string };