major: Implement 3-tiered testing architecture

see [docs/testing.md](./docs/testing.md)

vitest.config.evals.ts

@@ -0,0 +1,8 @@
+import { defineConfig } from "vitest/config";
+
+export default defineConfig({
+  test: {
+    include: ["tests/evals/**/*.eval.ts"],
+    exclude: ["**/node_modules/**", "**/dist/**"]
+  }
+});