Pin Node.js version in size report workflow

Adds setup-node to size.yml so it doesn't rely on whatever
Node ships on ubuntu-latest, consistent with the other workflows.

Made-with: Cursor

Author: Kamirus

.github/workflows/size.yml

@@ -7,6 +7,10 @@ jobs:
       CI_JOB_NUMBER: 1
     steps:
       - uses: actions/checkout@v4
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 'lts/*'
+          cache: 'npm'
       - run: npm ci
       - uses: andresz1/size-limit-action@v1
         with: