`cmake --build build --target doc` runs Doxygen to produce XML, then
`doc/gen_api_md.py` (~330 lines, stdlib-only) emits a Markdown tree
under `doc/api/` that gitea renders directly in its file browser.
- 24 class/struct pages + 51 source-file pages + indices, with source
links of the form `../../../../src/...#L42` that gitea turns into
clickable line-anchored links.
- Doxyfile.in templated by CMake (XML-only output to build/doc/xml/).
- Pure Python emitter, zero external deps — no doxybook2 (not packaged
on Arch) and no moxygen (avoids Node).
- Target gracefully disabled if Doxygen or Python 3 is missing at
configure time; regular build target unaffected.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
