ci: migrate from CircleCI to GitHub Actions

CircleCI has been unable to check out the repository since its checkout
key stopped working, so nothing has been deployed since 2023-10. Replace
it with GitHub Actions and publish through the Pages deployment API
instead of committing the build output to the master branch.

- add .github/workflows/deploy.yml (build on every push/PR, deploy to
  Pages on source)
- drop .circleci/config.yml and update.sh
- drop rimraf and status-back, only used by the two files above
- bump .node-version from 8.1.4 to 24, the current LTS
- fix bulbofile.js for the ESM majors of gulp-nunjucks and gulp-markdown
  pulled in by #312 and #313, which broke the build
- emit CNAME into build/ so the custom domain survives in the artifact

Author: kt3k

.circleci/config.yml

@@ -0,0 +1,46 @@
+name: build & deploy
+
+on:
+  push:
+    branches: [source]
+  pull_request:
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+# Let a running deploy finish rather than cancelling it half way.
+concurrency:
+  group: pages
+  cancel-in-progress: false
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v7
+      - uses: actions/setup-node@v7
+        with:
+          node-version-file: .node-version
+          cache: npm
+      - run: npm ci
+      - run: npm run build
+      # Uploaded on pull requests too, so the built site can be downloaded
+      # from the run page for review.
+      - uses: actions/upload-pages-artifact@v5
+        with:
+          path: build
+
+  deploy:
+    needs: build
+    if: github.event_name != 'pull_request'
+    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/deploy.yml

@@ -1 +1 @@
-8.1.4
+24

.node-version

@@ -3,8 +3,10 @@ const asset = bulbo.asset
 
 const path = require('path')
 const frontMatter = require('gulp-front-matter')
-const nunjucks = require('gulp-nunjucks')
-const markdown = require('gulp-markdown')
+// gulp-nunjucks v6 / gulp-markdown v8 are ESM. require() of ESM is supported
+// on Node 22.12+ so we read the named / default exports off the namespace.
+const {nunjucksCompile} = require('gulp-nunjucks')
+const markdown = require('gulp-markdown').default
 const wrapper = require('layout-wrapper')
 const accumulate = require('vinyl-accumulate')
 const branch = require('branch-pipe')
@@ -35,7 +37,7 @@ const layout = defaultLayout => wrapper.nunjucks({
 asset('source/**/*.md', '!source/{events,jobs,news}/**/*')
   .watch('source/**/*.{md,njk}')
   .pipe(frontMatter({property: 'fm'}))
-  .pipe(nunjucks.compile(data))
+  .pipe(nunjucksCompile(data))
   .pipe(markdown())
   .pipe(layout('default'))
 
@@ -128,3 +130,6 @@ asset('source/pdfs/**/*.pdf')
 
 // Old site is available under http://nodejs.jp/old/
 asset('./old/*.*').base('./')
+
+// The custom domain needs to be part of the published artifact
+asset('./CNAME').base('./')