test(01-02): add vitest.config.ts

- Node-environment test runner (Blob shimmed via undici in Vitest 4+)
- Scoped include: tests/**/*.test.ts (production code never picked up)
- typecheck disabled — tsc --noEmit runs separately via npm run build
- No path aliases (tsconfig.json defines none; relative imports used)

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

vitest.config.ts

@@ -0,0 +1,12 @@
+import { defineConfig } from 'vitest/config';
+
+export default defineConfig({
+  test: {
+    environment: 'node',
+    include: ['tests/**/*.test.ts'],
+    reporters: 'dot',
+    typecheck: {
+      enabled: false,
+    },
+  },
+});