ci: drop Node 16, bump actions to v4

Node 16 is EOL. Modern vitest/vite requires crypto.getRandomValues
(Node 19+). Test matrix now 18.x + 20.x. Bump checkout and
setup-node actions from v3 to v4.

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

Author: vveerrgg

.github/workflows/ci.yml

@@ -11,12 +11,12 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        node-version: [16.x, 18.x, 20.x]
+        node-version: [18.x, 20.x]
 
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
     - name: Use Node.js ${{ matrix.node-version }}
-      uses: actions/setup-node@v3
+      uses: actions/setup-node@v4
       with:
         node-version: ${{ matrix.node-version }}
         cache: 'npm'
@@ -27,9 +27,9 @@ jobs:
   security:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v3
-    - uses: actions/setup-node@v3
+    - uses: actions/checkout@v4
+    - uses: actions/setup-node@v4
       with:
-        node-version: 18
+        node-version: 20
         cache: 'npm'
     - run: npm audit

.github/workflows/documentation.yml

@@ -11,12 +11,12 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-    - uses: actions/checkout@v3
-    
+    - uses: actions/checkout@v4
+
     - name: Use Node.js
-      uses: actions/setup-node@v3
+      uses: actions/setup-node@v4
       with:
-        node-version: '18.x'
+        node-version: '20.x'
         cache: 'npm'
 
     - name: Install dependencies

.github/workflows/publish.yml

@@ -8,10 +8,10 @@ jobs:
   build:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
-      - uses: actions/setup-node@v3
+      - uses: actions/checkout@v4
+      - uses: actions/setup-node@v4
         with:
-          node-version: '18.x'
+          node-version: '20.x'
           registry-url: 'https://registry.npmjs.org'
       - run: npm ci
       - run: npm test