An incremental rebuild engine for the dev server — the release that made
docgen dev feel immediate on a large site, by rebuilding what a change actually
touched instead of the whole site on every keystroke.
Cross-document features make this genuinely hard: a change is only safely local
if nothing else depends on it. That constraint is why the engine has to reason
about staleness rather than just diff file contents, and it is why a later
feature like Bases has to force a full rebuild whenever a
.base consumes the corpus.
Windows left the release matrix in this cycle: the katex crate's default
quick-js backend does not compile on the MSVC target.