fix: move ajv to dependencies and add .yarnrc.yml for node-modules linker

ajv was in devDependencies but required at runtime by scripts/lib/install/config.js,
causing 'Cannot find module ajv' when running ./install.sh. Also adds .yarnrc.yml
with nodeLinker: node-modules so plain `node` can resolve packages without PnP.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

package.json

@@ -110,11 +110,11 @@
   },
   "dependencies": {
     "@iarna/toml": "^2.2.5",
+    "ajv": "^8.18.0",
     "sql.js": "^1.14.1"
   },
   "devDependencies": {
     "@eslint/js": "^9.39.2",
-    "ajv": "^8.18.0",
     "c8": "^10.1.2",
     "eslint": "^9.39.2",
     "globals": "^17.1.0",
@@ -122,5 +122,6 @@
   },
   "engines": {
     "node": ">=18"
-  }
+  },
+  "packageManager": "yarn@4.9.2+sha512.1fc009bc09d13cfd0e19efa44cbfc2b9cf6ca61482725eb35bbc5e257e093ebf4130db6dfe15d604ff4b79efd8e1e8e99b25fa7d0a6197c9f9826358d4d65c3c"
 }