The README says a plugin folder holds "an index.html for previewing it", and a fresh reader
followed that to /plugin-designs/<plugin>/index.html under `bun run dev`. leafRewrite reads any
<a>/<b>/index.html as <bundle>/<profile>, so the request reached the leaf route as bundle
"plugin-designs" and answered only {"error":"unknown bundle"}, which pointed nowhere.
The 404 now carries a hint: for a folder that is a plugin, its own page
(/__leaf/all-people-groups/all-people-groups, taken from the same registry the gallery uses);
otherwise the /__leaf/<plugin>/<profile> shape and the manifest that lists every plugin. The
status and the error stay as they were. The README now names the page as well.
f8828a2094