The native docs development server returns 404 for existing WebP and AVIF files because its static extension list omits both formats. Include them in the existing public-first/docs-root lookup, matching the formats already supported by build preview.
A real HTTP regression failed before the change with the existing WebP asset returning 404, then passed with 41 assertions covering both lookup roots, configured docs mount and unmounted paths, MIME types, exact bytes, public-file precedence, missing assets, existing source-link rendering and public asset copying during native build. Full native suite: 596 passed, 0 failed, 1,772 assertions across 47 files. Native build, types and Pickier pass; two pre-existing lint warnings are unchanged.
Refs #89. This source fix does not upgrade an application graph or claim that a compatible release has been adopted.