docs: the Antora component is never built, and docs-only pull requests get no check #114

The Antora component in docs/ is not published anywhere yet: https://docs.arcadedb.com/arcadedb-python/ returns 404, and adding the component as a content source is still open in ArcadeData/arcadedb-docs#505 (since 2026-10-23). Until then, nobody can read a page as it renders, and nothing builds the pages at all:

• The test workflows ignore docs/** and *.adoc, so a docs-only pull request gets no check. A broken xref:, a misspelled {attribute} (it renders as written) or an AsciiDoc syntax error ships unseen.
• The component cannot build on its own: 13 links use xref:arcadedb::..., which resolves only inside the full docs.arcadedb.com build.

Proposed: link into the main manual through one attribute ({arcadedb-docs-url}/<page>, checked live: all 10 target pages and 4 anchors exist), add a standalone Antora playbook with the same UI and asciidoc attributes as docs.arcadedb.com, and a Docs workflow that builds it on every change under docs/ (a warning fails it) and attaches the site as an artifact. Hosting the built site is a separate step: GitHub Pages on this repository would serve it at arcadedata.com/arcadedb-python/, because the org site has that custom domain.