chore: align packageManager and engines fields across repos

- Change packageManager to exact version: pnpm@10.21.0 (Corepack requires exact semver)
- Standardize engines.node to >=18 (align with other Socket repos)
- Add engines.pnpm: >=10.21.0 for consistency

Author: jdalton

package.json

@@ -1,7 +1,7 @@
 {
   "name": "@socketsecurity/lib",
   "version": "3.3.0",
-  "packageManager": "pnpm@>=10.21.0",
+  "packageManager": "pnpm@10.21.0",
   "license": "MIT",
   "description": "Core utilities and infrastructure for Socket.dev security tools",
   "keywords": [
@@ -579,7 +579,8 @@
     "CHANGELOG.md"
   ],
   "engines": {
-    "node": ">=22"
+    "node": ">=18",
+    "pnpm": ">=10.21.0"
   },
   "sideEffects": false,
   "scripts": {