docs: automated documentation pipeline (per-symbol source → pages)

Replace the hardcoded landing page and minimal reference with a generated
documentation site driven by a single source of truth.

- docs/language/**: one file per symbol (93 keywords/types/builtins/namespace
  methods/operators/annotations), each with front-matter (id, kind, tokens,
  sig, tip) + description + a ```ludic example. Seeded by exploding the former
  inline SECTIONS list; these files are now the source of truth.
- docs/site/: site.json (editable hero/features/showcase/messaging, not
  hardcoded) + snippets/*.ludic (real programs shown on the landing page).
- tools/docgen/gen.py: generates index.html, api.html, ludic-highlight.js and
  symbols.json. The highlighter's symbol tables, hover tips and jump anchors
  are GENERATED from the per-symbol files — add a symbol and it is recognized,
  tipped and linked in every snippet automatically. Python stdlib only.
- tools/docgen/check.py: verifies the pages contract + that no snippet token
  links to a missing reference anchor.
- .forgejo/workflows/docs.yml: rebuilds and publishes to the pages branch on
  every push to main touching the docs sources.

Consumes the new Screen.*/Color.*/named-arg API and the 221-color palette.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.forgejo/workflows/docs.yml

@@ -0,0 +1,55 @@
+name: docs
+
+# Rebuild the documentation site and publish it to the `pages` branch on every
+# push to main that touches the docs sources. The site is generated from the
+# per-symbol source of truth in docs/language/** — nothing is hand-edited on the
+# pages branch.
+on:
+  push:
+    branches: [main]
+    paths:
+      - 'docs/**'
+      - 'tools/docgen/**'
+      - '.forgejo/workflows/docs.yml'
+  workflow_dispatch: {}
+
+permissions:
+  contents: write
+
+jobs:
+  build-and-deploy:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Generate the documentation site
+        run: |
+          python3 --version
+          python3 tools/docgen/gen.py --out public
+          echo "--- generated files ---"
+          ls -la public
+
+      - name: Sanity-check the output (root has index.html + .nojekyll, no broken links)
+        run: python3 tools/docgen/check.py public
+
+      - name: Publish to the pages branch
+        run: |
+          set -eu
+          TOKEN="${PAGES_TOKEN:-${AUTO_TOKEN:-}}"
+          if [ -z "$TOKEN" ]; then
+            echo "::error::No deploy token. Add a repo secret PAGES_TOKEN (write access) or allow the automatic token to push."
+            exit 1
+          fi
+          cd public
+          git init -q -b pages
+          git config user.name  "ludic-docs-bot"
+          git config user.email "docs@workshopsoft.io"
+          git add -A
+          git commit -q -m "docs: regenerate site from ${SOURCE_SHA}"
+          git push -f "https://ludic-docs-bot:${TOKEN}@git.workshopsoft.io/workshopsoft/ludic.git" pages
+          echo "published $(git rev-parse --short HEAD) to pages"
+        env:
+          PAGES_TOKEN: ${{ secrets.PAGES_TOKEN }}
+          AUTO_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          SOURCE_SHA: ${{ github.sha }}