fix: configure setup-node for npm OIDC trusted publishing

Bump actions/setup-node to v6 and add registry-url so npm can
authenticate via GitHub OIDC for trusted publishing with provenance.
Without registry-url, npm publish fails with ENEEDAUTH.

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

Author: pRizz

.github/workflows/publish-npm.yml

@@ -44,9 +44,10 @@ jobs:
         uses: Swatinem/rust-cache@v2
 
       - name: Setup Node.js
-        uses: actions/setup-node@v5
+        uses: actions/setup-node@v6
         with:
           node-version: '24'
+          registry-url: 'https://registry.npmjs.org'
 
       - name: Setup Bun
         uses: ./.github/actions/setup-bun