OSS: linkify @-mentions, drop dead workspace-folder refs

@username mentions across all entries now point to https://github.com/<user>
instead of rendering as plain text on the published Jekyll page.

Folder: refs (e.g. ./dask-11270) were dead links — those workspace folders
are local-only, not published. Dropped them; for urllib3#4989 replaced
with a direct link to the upstream changelog file.

Author: xronocode