ci: publish to npm via OIDC Trusted Publishing

Switch the npm publish workflow from a long-lived NPM_TOKEN secret to
short-lived OIDC tokens via npm Trusted Publishing. Grant id-token: write,
upgrade npm to @latest (Trusted Publishing needs npm >= 11.5.1), drop
NODE_AUTH_TOKEN, and add --provenance for attestation.

Required setup on npmjs.com before the next release tag:
1. npmjs.com -> @snap/react-camera-kit settings -> Publishing access ->
   Add trusted publisher -> GitHub Actions
2. Org: Snapchat, Repo: react-camera-kit, Workflow filename: publish.yml,
   Environment: blank
3. After the first successful OIDC publish, delete the NPM_TOKEN repo secret.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: msilivonik-sc

.github/workflows/publish.yml

@@ -10,6 +10,9 @@ jobs:
   publish:
     runs-on: ubuntu-latest
     timeout-minutes: 10
+    permissions:
+      contents: read
+      id-token: write
     steps:
       - name: Checkout code
         uses: actions/checkout@v4
@@ -21,6 +24,9 @@ jobs:
           cache: npm
           registry-url: "https://registry.npmjs.org/"
 
+      - name: Upgrade npm for Trusted Publishing
+        run: npm install -g npm@latest
+
       - name: Determine pre-release tag
         run: |
           TAG_NAME=${GITHUB_REF_NAME}
@@ -50,6 +56,4 @@ jobs:
         run: npm run build
 
       - name: Publish
-        run: npm publish --access public --tag ${{ env.tag }}
-        env:
-          NODE_AUTH_TOKEN: ${{ secrets.NPM_TOKEN }}
+        run: npm publish --provenance --access public --tag ${{ env.tag }}