major: Implement 3-tiered testing architecture

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

package.json

@@ -13,7 +13,10 @@
     "lint:fix": "eslint . --fix",
     "format": "prettier . --write",
     "format:check": "prettier . --check",
-    "watch": "tsc -b --watch"
+    "watch": "tsc -b --watch",
+    "test": "vitest run",
+    "test:watch": "vitest",
+    "test:evals": "vitest run --config vitest.config.evals.ts"
   },
   "keywords": [],
   "author": "",
@@ -36,6 +39,7 @@
     "prettier": "^3.9.4",
     "typescript": "^6.0.3",
     "typescript-eslint": "^8.62.1",
+    "vitest": "^4.1.9",
     "zod": "^4.4.3"
   },
   "dependencies": {