test(frontend): add comprehensive test coverage for Phase 3

- Add AI component tests (ContextConfigEditor, PromptEditor, RuntimeParametersPanel, SandboxTabs, VersionHistory)
- Add layout component tests (GlobalSearch, NotificationsDropdown, ProjectSwitcher, Sidebar, UserMenu)
- Update vitest.setup.ts for better test configuration
- Update .gitignore to exclude test artifacts
- All 722 tests passing

frontend/vitest.setup.ts

@@ -87,3 +87,8 @@ if (!Element.prototype.setPointerCapture) {
 if (!Element.prototype.releasePointerCapture) {
   Element.prototype.releasePointerCapture = () => {};
 }
+
+// Mock scrollIntoView for cmdk component
+if (!Element.prototype.scrollIntoView) {
+  Element.prototype.scrollIntoView = vi.fn();
+}