test(worker): add vitest harness

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

worker/src/archive/fingerprint.test.ts

@@ -0,0 +1,7 @@
+import { describe, it, expect } from "vitest";
+
+describe("harness", () => {
+  it("runs", () => {
+    expect(1 + 1).toBe(2);
+  });
+});