fix(test): use globalThis instead of global for fetch mock

Replace Node.js-specific 'global' with standard 'globalThis' for
cross-environment compatibility in TypeScript compilation.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: aledlie

src/test/setup.ts

@@ -59,7 +59,7 @@ class IntersectionObserverMock {
 window.IntersectionObserver = IntersectionObserverMock;
 
 // Mock fetch
-global.fetch = vi.fn();
+globalThis.fetch = vi.fn();
 
 // Clean up after each test
 afterEach(() => {