Add CI, release, and Pages workflows with Dependabot

- ci.yml: typecheck, tests, and pack check on Ubuntu (Node 22, 24, 26), macOS and Windows (Node 24)
- release.yml: tag vX.Y.Z reruns CI, checks tag, package.json and CHANGELOG agree, publishes with npm trusted publishing, and creates the GitHub Release
- pages.yml: deploys site/ to GitHub Pages
- Jobs run on GitHub only; the Gitea origin's runner skips them
- Dependabot proposes grouped npm and Actions updates weekly

.github/dependabot.yml

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+version: 2
+updates:
+  - package-ecosystem: npm
+    directory: /
+    schedule:
+      interval: weekly
+    cooldown:
+      default-days: 7
+    groups:
+      dev-dependencies:
+        dependency-type: development
+    ignore:
+      # TypeScript 7 ships no tsserver.js, which editors and typescript-language-server still need.
+      - dependency-name: typescript
+        update-types: ["version-update:semver-major"]
+      # @types/node tracks the oldest Node version CI tests (22).
+      - dependency-name: "@types/node"
+        update-types: ["version-update:semver-major"]
+
+  - package-ecosystem: github-actions
+    directory: /
+    schedule:
+      interval: weekly
+    cooldown:
+      default-days: 7
+    groups:
+      actions:
+        patterns: ["*"]

.github/scripts/changelog-section.mjs

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+#!/usr/bin/env node
+// Prints the CHANGELOG.md section for a version (used as GitHub Release notes).
+// Fails when the section is missing or still marked "Unreleased", so a release cannot ship undated notes.
+import { readFileSync } from 'node:fs';
+
+const version = process.argv[2];
+if (!version) {
+  console.error('Usage: changelog-section.mjs <version>');
+  process.exit(2);
+}
+
+const lines = readFileSync(new URL('../../CHANGELOG.md', import.meta.url), 'utf8').split('\n');
+const escaped = version.replace(/[.*+?^${}()|[\]\\]/g, '\\$&');
+const start = lines.findIndex((line) => new RegExp(`^## ${escaped}(\\s|$)`).test(line));
+
+if (start === -1) {
+  console.error(`CHANGELOG.md has no "## ${version}" section.`);
+  process.exit(1);
+}
+if (/unreleased/i.test(lines[start] ?? '')) {
+  console.error(`CHANGELOG.md section "${lines[start]}" is still marked Unreleased; replace it with the release date.`);
+  process.exit(1);
+}
+
+const end = lines.findIndex((line, index) => index > start && line.startsWith('## '));
+const body = lines.slice(start + 1, end === -1 ? undefined : end).join('\n').trim();
+process.stdout.write(`${body}\n`);

.github/workflows/ci.yml

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+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+  workflow_call:
+
+permissions:
+  contents: read
+
+concurrency:
+  group: ci-${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  test:
+    name: Test (${{ matrix.os }}, Node ${{ matrix.node }})
+    # GitHub only: the Gitea origin also runs .github/workflows but has no macOS/Windows runners.
+    if: github.server_url == 'https://github.com'
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest]
+        node: [22, 24, 26]
+        include:
+          - os: macos-latest
+            node: 24
+          - os: windows-latest
+            node: 24
+    env:
+      HUSKY: "0"
+    steps:
+      - uses: actions/checkout@v7
+      - uses: actions/setup-node@v7
+        with:
+          node-version: ${{ matrix.node }}
+          cache: npm
+      - run: npm ci
+      - run: npm run typecheck
+      - run: npm test
+      - name: Check package contents
+        run: npm pack --dry-run

.github/workflows/pages.yml

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+name: Pages
+
+on:
+  push:
+    branches: [main]
+    paths:
+      - "site/**"
+      - ".github/workflows/pages.yml"
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+concurrency:
+  group: pages
+  cancel-in-progress: false
+
+jobs:
+  build:
+    name: Build site
+    # GitHub only: the Gitea origin also runs .github/workflows but has no Pages; deploy skips with this job.
+    if: github.server_url == 'https://github.com'
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v7
+      - uses: actions/configure-pages@v6
+      - name: Stage site without source notes
+        run: rsync -a --exclude='*.md' site/ _site/
+      - uses: actions/upload-pages-artifact@v5
+        with:
+          path: _site/
+
+  deploy:
+    name: Deploy
+    needs: build
+    runs-on: ubuntu-latest
+    permissions:
+      pages: write
+      id-token: write
+    environment:
+      name: github-pages
+      url: ${{ steps.deployment.outputs.page_url }}
+    steps:
+      - id: deployment
+        uses: actions/deploy-pages@v5

.github/workflows/release.yml

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+name: Release
+
+# Push a vX.Y.Z tag after bumping package.json and dating the CHANGELOG section.
+# Publishing uses npm trusted publishing (OIDC): no npm token is stored in this repository.
+
+on:
+  push:
+    tags: ["v*.*.*"]
+
+permissions:
+  contents: read
+
+concurrency:
+  group: release-${{ github.ref }}
+  cancel-in-progress: false
+
+jobs:
+  verify:
+    name: Verify
+    # GitHub only: npm trusted publishing needs GitHub's OIDC token; later jobs skip with this one.
+    if: github.server_url == 'https://github.com'
+    uses: ./.github/workflows/ci.yml
+
+  publish:
+    name: Publish to npm
+    needs: verify
+    runs-on: ubuntu-latest
+    environment: npm
+    permissions:
+      contents: read
+      id-token: write
+    env:
+      HUSKY: "0"
+    steps:
+      - uses: actions/checkout@v7
+      - uses: actions/setup-node@v7
+        with:
+          node-version: 24
+          registry-url: https://registry.npmjs.org
+          package-manager-cache: false
+      - name: Use npm 12 (trusted publishing needs 11.5.1 or later)
+        run: npm install -g npm@12
+      - name: Check tag, package.json, and CHANGELOG agree
+        run: |
+          version="${GITHUB_REF_NAME#v}"
+          package_version="$(node -p "require('./package.json').version")"
+          if [ "$version" != "$package_version" ]; then
+            echo "::error::Tag $GITHUB_REF_NAME does not match package.json version $package_version"
+            exit 1
+          fi
+          node .github/scripts/changelog-section.mjs "$version" > /dev/null
+      - run: npm ci
+      - run: npm run build
+      - name: Publish
+        run: |
+          version="${GITHUB_REF_NAME#v}"
+          if [[ "$version" == *-* ]]; then
+            npm publish --access public --tag next
+          else
+            npm publish --access public
+          fi
+
+  github-release:
+    name: GitHub Release
+    needs: publish
+    runs-on: ubuntu-latest
+    permissions:
+      contents: write
+    steps:
+      - uses: actions/checkout@v7
+      - name: Create release from CHANGELOG
+        env:
+          GH_TOKEN: ${{ github.token }}
+        run: |
+          version="${GITHUB_REF_NAME#v}"
+          node .github/scripts/changelog-section.mjs "$version" > release-notes.md
+          prerelease=""
+          if [[ "$version" == *-* ]]; then prerelease="--prerelease"; fi
+          gh release create "$GITHUB_REF_NAME" --verify-tag --title "$GITHUB_REF_NAME" --notes-file release-notes.md $prerelease