Add setup-node step for npm registry auth (#8)

setup-node with registry-url configures the .npmrc with the OIDC
token needed for trusted publishing via bunx npm publish.

Co-authored-by: Ona <no-reply@ona.com>

.github/workflows/publish.yml

@@ -19,6 +19,11 @@ jobs:
 
       - uses: oven-sh/setup-bun@v2
 
+      - uses: actions/setup-node@v4
+        with:
+          node-version: '24'
+          registry-url: 'https://registry.npmjs.org'
+
       - run: bun install
 
       - run: bun run build