chore: bump actions/setup-node v4→v6 and actions/checkout v4→v6

Author: crisconru

.github/workflows/publish.yml

@@ -47,7 +47,7 @@ jobs:
           git clone --depth 1 --branch "${{ steps.vars.outputs.tag }}" \
             https://codeberg.org/crisconru/schemasjs.git source
 
-      - uses: actions/setup-node@v4
+      - uses: actions/setup-node@v6
         with:
           node-version: "24"
           registry-url: "https://registry.npmjs.org"

.github/workflows/sync-stub.yml

@@ -17,7 +17,7 @@ jobs:
     permissions:
       contents: write
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Resolve source ref
         id: vars