Adds .forgejo/workflows/build-slides.yml triggering on push to main and
manual dispatch. Job runs in node:20-bookworm-slim, installs marp-cli +
python3, mounts /srv/slides/html into /output, and invokes
build-slides.sh with OUTPUT_DIR=/output.
build-slides.sh now honors OUTPUT_DIR/SLIDES_TITLE/REPO_WEB_URL env
overrides (defaults preserve local-dev behavior), wipes stale .html
before each build, and regenerates a styled index.html listing every
deck — replacing the equivalent logic from the old webhook update.sh.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
