Add CI build verification and release workflow

Add a dedicated build job to the CI workflow that verifies the
Vite build succeeds on every push to main and PR. This runs in
parallel with the existing check job.

Add release.yml workflow triggered on GitHub release publication.
It runs npm ci, npm run build, and npm publish with --provenance
(SLSA provenance attestation) and --access public (required for
@ably/ scoped packages). Uses the NPM_TOKEN repository secret
for authentication via setup-node's registry-url configuration.

Author: VeskeR

.github/workflows/release.yml

@@ -0,0 +1,27 @@
+name: Release packages
+
+on:
+  release:
+    types: [published]
+
+jobs:
+  release:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: 'write'
+      id-token: 'write'
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          submodules: true
+      - uses: actions/setup-node@v4
+        with:
+          node-version: '24'
+          registry-url: 'https://registry.npmjs.org'
+      - name: Install dependencies and publish
+        env:
+          NODE_AUTH_TOKEN: ${{ secrets.NPM_TOKEN }}
+        run: |
+          npm ci
+          npm run build
+          npm publish --provenance --access public

.github/workflows/test.yml

@@ -31,3 +31,19 @@ jobs:
       - run: npm run check:error-codes
       - run: npm test
       - run: npm run test:integration
+
+  build:
+    name: Build
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          submodules: true
+
+      - uses: actions/setup-node@v6
+        with:
+          node-version: 24.x
+          cache: npm
+
+      - run: npm ci
+      - run: npm run build