chore(config): pin @types/bun, tighten TypeScript strictness, and refactor config logic

- Pin `@types/bun` to `^1.3.14` for reproducible builds instead of using `latest`
- Update `tsconfig.json` with stricter type-checking flags and reorganize compiler options
- Refactor `initConfig` to DRY up the model default logic and add a null guard before process exit

package.json

@@ -18,7 +18,7 @@
   },
   "devDependencies": {
     "@biomejs/biome": "2.4.12",
-    "@types/bun": "latest",
+    "@types/bun": "^1.3.14",
     "esbuild": "0.28.0"
   },
   "peerDependencies": {