fix(plugins/reports): wire @testing-library/react cleanup so React teardown doesn't leak past test env

The api stub from 43be32bbd silenced the fetch-rejection path but the suite
still failed on CI: the actual unhandled error is React's scheduler firing
deferred work via setImmediate after jsdom is torn down — its internal
render then dereferences `window` and throws ReferenceError. @testing-library
only auto-registers cleanup() when vitest `globals: true` is set, and this
package doesn't enable globals, so the React tree from each render() stays
mounted across teardown. Register cleanup manually in test-setup.ts so every
dashboard test unmounts its tree before the environment tears down.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

plugins/fusion-plugin-reports/src/dashboard/test-setup.ts

@@ -1,5 +1,13 @@
 import "@testing-library/jest-dom/vitest";
-import { vi } from "vitest";
+import { cleanup } from "@testing-library/react";
+import { afterEach, vi } from "vitest";
+
+// @testing-library/react only auto-registers cleanup when vitest globals are
+// enabled. We don't enable globals here, so we wire it manually — otherwise
+// React leaves the test tree mounted, its scheduler fires a deferred update
+// via setImmediate after the jsdom environment is torn down, and the suite
+// fails with "ReferenceError: window is not defined".
+afterEach(() => cleanup());
 
 if (typeof window !== "undefined") {
   Object.defineProperty(window, "matchMedia", {