docs: move the documentation from MkDocs to AsciiDoc, published on smallrye.io

[phillip-kruger]

The docs move from MkDocs to AsciiDoc, laid out like the Quarkus guides. smallrye.io pulls them in and publishes them at https://smallrye.io/docs/smallrye-mutiny// (smallrye/smallrye.github.io#136): main nightly, each release once it is tagged. smallrye.io already publishes 3.3.0's docs, converted on the fly, so nothing waits for this PR.

Depends on smallrye/smallrye.github.io#136. The new Documentation check calls the reusable workflow added there.

What changes

• Pages. documentation/docs/**/*.md become documentation/src/main/asciidoc/**/*.adoc, with the same paths, so the same addresses.
  • The sidebar is in _nav.yml and shared attributes are in _attributes.adoc.
  • Ids are Quarkus-style.
• Versions. The Mutiny and Vert.x bindings versions live in _versions.adoc. .build/UpdateDocsAttributesFiles.java, run by just prepare-release, now writes it instead of attributes.yaml.
• Code examples stay tests in documentation/src/test and still compile and run (149 tests pass). Pages include them with include::{examples-dir}/...[tags=...], and the docissimo // <tag> markers become // tag::tag[] / // end::tag[]. Only comment lines change.
• Tags. Page tags are kept as :topics:, and tags-index lists the pages per tag.
• PR check. Pull requests touching documentation/ run the new Documentation workflow. It renders the docs with the smallrye.io site, fails on a broken include or a page that does not render, and attaches the rendered site as an artifact. It replaces the MkDocs check in build-pull.yml.
• Removed: mkdocs.yml, the macros, the uv/Python project, and the mike Manual website deployment workflow.
• Docs and links. documentation/README.adoc explains how to write and preview pages, and the README, math/README.md and pom links point to the new location.

Older versions

Everything already on gh-pages stays where it is, and the site's version picker links to it as "Older versions". After this is merged, the mike latest alias and the root page on gh-pages will redirect to /docs/smallrye-mutiny/latest/.

Checked

• All 56 pages render with the smallrye.io site, with no errors or Asciidoctor warnings.
• All 4,482 internal links resolve.
• mvn -pl documentation test passes.

[phillip-kruger]

Screenshots of the documentation before and after this change (updated).

Before: the MkDocs site, as it is on smallrye.io today. After: this branch's AsciiDoc, rendered by smallrye.io with smallrye/smallrye.github.io#136 (a local build: /docs/smallrye-mutiny/main/). On smallrye.io the sidebar starts closed (the ☰ button opens it, and it stays open on the next pages for that reader); its groups are folded except the one holding the current page. The project and version picker sit in the header next to the logo, so a start page has no separate title; further down, a start page lists the documentation, from its navigation.

Before	After
Home page · old page
How to handle timeouts? · old page
How to handle timeouts?, with the Contents sidebar open
Observing events (Mermaid diagram) · old page
Dark theme (smallrye-mutiny): light paper behind the drawing (before) and its dark version (after)

Dark theme: the same screenshots with the dark theme

The old Antora sites and the GraphQL, Vert.x bindings and Mutiny Zero MkDocs sites have no dark theme, so their "before" stays light; the other old MkDocs sites were switched to their own dark palette.

Before (dark theme)	After (dark theme)
Home page · old page
How to handle timeouts? · old page
How to handle timeouts?, with the Contents sidebar open
Observing events (Mermaid diagram) · old page