feat: establish TypeScript-aware frontend tooling

tests/unit/typescript-tooling-smoke.test.ts

@@ -0,0 +1,16 @@
+import { describe, expect, it } from "vitest";
+
+type Result<T, E> =
+  | Readonly<{ ok: true; value: T }>
+  | Readonly<{ ok: false; error: E }>;
+
+function summarize(result: Result<number, string>): string {
+  return result.ok ? String(result.value) : result.error;
+}
+
+describe("TypeScript test tooling", () => {
+  it("type-checks and executes discriminated unions in the test project", () => {
+    expect(summarize({ ok: true, value: 42 })).toBe("42");
+    expect(summarize({ ok: false, error: "failed" })).toBe("failed");
+  });
+});