tatara-doc — catalog browser over the registered domains.
Walks the three capability registries
(registered_keywords, registered_render_keywords,
registered_doc_keywords) and emits a stable Markdown
catalog page. Same data the IDE hover-help would use; same
data a tatara doc CLI subcommand would print; same data a
web view would render.
What this proves
Three capability registries are now visible to a single consumer at once. Every new domain that registers itself with the standard six-line contract gets a free catalog entry with no edits to this crate. That's "compounding systems on top of each other" made operational — each layer (compile / render / doc) contributes; this crate just unions.