fix: remove Node.js 18.x from CI matrix

Vite 7.x requires Node.js 20.19+ or 22.12+, so Node.js 18.x is no longer supported.

Author: seijikohara

.github/workflows/npm-ci.yml

@@ -8,7 +8,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        node-version: [18.x, 20.x, 22.x, 24.x]
+        node-version: [20.x, 22.x, 24.x]
     steps:
       - uses: actions/checkout@v4
       - name: Use Node.js ${{ matrix.node-version }}