doc: repair the cross-reference to the Registry affinity section

[jll63]

(Written by Claude Code, on behalf of @jll63.)

Found by rendering the docs; nothing in the build fails on it.

#111 added see <<Registry affinity>> below to registries_and_policies.adoc and
hard-wrapped it at the 79-column margin, which put a newline inside the macro:

the classes involved declare no affinity of their own - see <<Registry
affinity>> below.

Asciidoctor does not match a title reference across the break, so it fell back to
the unresolved form. The page rendered

see <a href="#Registry affinity">[Registry affinity]</a> below.

• a literal [Registry affinity] in square brackets, pointing at a fragment with a
  space in it, which matches no anchor. The section's own id is the generated
  _registry_affinity, so the link was dead in both directions.

The build does say so - possible invalid reference: Registry\naffinity - but the
line sits among the section-title-out-of-sequence warnings, the job still passes,
and the rendered sentence looks plausible enough to read past.

Fixed with an explicit anchor, which is what the page's siblings already use:
<<custom_registries>>, <<implementation_notes>> and
<<registering_classes_by_reflection>> each pair with a [#id] line above their
heading. That spelling survives rewrapping and does not break if the heading is
reworded.

Rebuilt to check: the link now renders as Registry affinity -> #registry_affinity,
and the build reports no invalid references.

While rendering I also cross-checked every @ref target in the headers against the
labels MrDocs turned into links, per the procedure in CLAUDE.md. All 110 resolve,
including the new ones from #103 and #110; grep -rl MRDOCS doc/html/ is empty.

🤖 Generated with Claude Code

[cppalliance-bot]

An automated preview of the documentation is available at https://119.openmethod.prtest3.cppalliance.org/libs/openmethod/doc/html/index.html

If more commits are pushed to the pull request, the docs will rebuild at the same URL.

2026-09-18 00:02:55 UTC