ci(pages): publish committed html/ folder to GitHub Pages [opencode:arc/apex]

- Workflow triggers on html/** changes to main (and workflow_dispatch),
  uploads the html/ folder as a Pages artifact and deploys it
- Un-ignore html/ so it can be committed as the published artifact
- README: add a Publishing to GitHub Pages section

Author: geoffroy-noel-ddh

.github/workflows/pages.yml

@@ -0,0 +1,48 @@
+name: Publish to GitHub Pages
+
+# Publishes the committed html/ folder to GitHub Pages.
+# The html/ folder is committed (it is not gitignored); regenerate it locally
+# by running `python main.py` whenever the source exhibition changes.
+
+on:
+  push:
+    branches: [main]
+    paths:
+      - 'html/**'
+      - '.github/workflows/pages.yml'
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+concurrency:
+  group: pages
+  cancel-in-progress: true
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Verify html/ exists
+        run: test -f html/index.html
+
+      - uses: actions/configure-pages@v5
+
+      - uses: actions/upload-pages-artifact@v3
+        with:
+          path: html
+
+  deploy:
+    needs: build
+    runs-on: ubuntu-latest
+    environment:
+      name: github-pages
+      url: ${{ steps.deploy.outputs.page_url }}
+    permissions:
+      pages: write
+      id-token: write
+    steps:
+      - id: deploy
+        uses: actions/deploy-pages@v4

.gitignore

@@ -21,4 +21,3 @@ env/
 
 # Output of the tool
 output/
-html/

README.md

@@ -38,6 +38,29 @@ With no arguments it mirrors the SHARC exhibition into `./html/`.
   URL so they still load when online. Re-run from an unrestricted network to
   fill them in.
 
+## Publishing to GitHub Pages
+
+The `html/` folder is committed to the repo (it is the published artifact).
+A workflow at `.github/workflows/pages.yml` publishes it to GitHub Pages
+whenever `html/**` changes on `main`:
+
+- In the repo **Settings → Pages → Build and deployment → Source**, select
+  **GitHub Actions**.
+- Push (or merge) a change under `html/` to `main`. The workflow uploads the
+  `html/` folder as a Pages artifact and deploys it. You can also run it
+  manually via the Actions tab (**workflow_dispatch**).
+
+To refresh the published mirror, regenerate it locally and commit the
+updated `html/` folder:
+
+```bash
+pip install -r requirements.txt
+python main.py
+git add html
+git commit -m "docs: refresh html mirror"
+git push
+```
+
 ## License
 
 MIT