feat: core types, time, rng, model fetch

Co-Authored-By: Claude Haiku 5.5 <[email protected]>

package.json

@@ -1,8 +1,13 @@
 {
   "name": "stsheets",
-  "module": "index.ts",
   "type": "module",
   "private": true,
+  "scripts": {
+    "test": "bun test",
+    "typecheck": "bunx tsc --noEmit",
+    "fetch-models": "bun scripts/fetch-models.ts",
+    "bench": "bun src/bench/cli.ts"
+  },
   "devDependencies": {
     "@types/bun": "latest"
   },