fix(ci): drop Node 18 support, require >=20 for vitest/rolldown compatibility

Author: bug3

.github/workflows/ci.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        node-version: [18, 20, 22]
+        node-version: [20, 22]
     steps:
       - uses: actions/checkout@v4
       - uses: actions/setup-node@v4

package.json

@@ -36,7 +36,7 @@
   ],
   "license": "MIT",
   "engines": {
-    "node": ">=18"
+    "node": ">=20"
   },
   "devDependencies": {
     "@eslint/js": "^9.39.4",