Add folder game, file browser UI, and automated tests.

Introduces a localStorage-backed messy-desktop challenge with sub-steps,
drag-and-drop and Places/Back navigation, IBM Plex Mono, and a /api/health
endpoint. Adds Vitest coverage for the API and level logic plus Playwright
smoke tests.

Made-with: Cursor

tests/unit/levels.test.ts

@@ -0,0 +1,52 @@
+import { describe, expect, it } from "vitest";
+
+import {
+  buildInitialFs,
+  isFsLevelComplete,
+  isQuizComplete,
+  isSubComplete,
+  QUIZ_CORRECT_ID,
+} from "~/lib/folder-game/levels";
+
+describe("isFsLevelComplete", () => {
+  it("level 0 completes when Games and Documents were opened", () => {
+    const fs = buildInitialFs(0);
+    expect(isFsLevelComplete(0, fs)).toBe(false);
+    expect(
+      isFsLevelComplete(0, {
+        ...fs,
+        visitedFolderIds: ["fld-games", "fld-docs"],
+      }),
+    ).toBe(true);
+  });
+
+  it("level 1 completes when files are sorted", () => {
+    const fs = buildInitialFs(1);
+    const nodes = fs.nodes.map((n) => {
+      if (n.id === "file-cat") return { ...n, parentId: "fld-pics" };
+      if (n.id === "file-hw") return { ...n, parentId: "fld-school" };
+      return n;
+    });
+    expect(isFsLevelComplete(1, { ...fs, nodes })).toBe(true);
+  });
+});
+
+describe("isSubComplete", () => {
+  it("level 0 sub 0 requires Games", () => {
+    const fs = buildInitialFs(0);
+    expect(isSubComplete(0, 0, fs)).toBe(false);
+    expect(
+      isSubComplete(0, 0, {
+        ...fs,
+        visitedFolderIds: ["fld-games"],
+      }),
+    ).toBe(true);
+  });
+});
+
+describe("isQuizComplete", () => {
+  it("accepts Documents choice", () => {
+    expect(isQuizComplete(QUIZ_CORRECT_ID)).toBe(true);
+    expect(isQuizComplete("opt-dl")).toBe(false);
+  });
+});