Add GitHub Actions CI and release workflows

.github/workflows/ci.yml

@@ -0,0 +1,40 @@
+name: CI
+
+on:
+  pull_request:
+    branches:
+      - main
+  push:
+    branches:
+      - main
+  workflow_dispatch:
+
+jobs:
+  build:
+    name: Build (Node ${{ matrix.node-version }})
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        node-version:
+          - 20
+          - 24
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: ${{ matrix.node-version }}
+          cache: npm
+
+      - name: Install dependencies
+        run: npm ci
+
+      - name: Build
+        run: npm run build
+
+      - name: Verify publish artifact
+        run: npm pack --dry-run

.github/workflows/release.yml

@@ -0,0 +1,47 @@
+name: Release
+
+on:
+  push:
+    tags:
+      - "v*"
+
+permissions:
+  contents: read
+  id-token: write
+
+jobs:
+  publish:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: 24
+          registry-url: https://registry.npmjs.org
+          cache: npm
+
+      - name: Ensure tag matches package version
+        run: |
+          PACKAGE_VERSION="$(node -p "require('./package.json').version")"
+          TAG_VERSION="${GITHUB_REF_NAME#v}"
+
+          if [ "$PACKAGE_VERSION" != "$TAG_VERSION" ]; then
+            echo "package.json version ($PACKAGE_VERSION) does not match tag ($TAG_VERSION)"
+            exit 1
+          fi
+
+      - name: Install dependencies
+        run: npm ci
+
+      - name: Build
+        run: npm run build
+
+      - name: Verify publish artifact
+        run: npm pack --dry-run
+
+      - name: Publish to npm
+        run: npm publish --access public