Adds two profile fields to users and orgs.
profile set --about <text> or --file - stores long-form text, with
--about-format md|org picking the renderer. profile set --link "label|url" repeats up to five times; a bare url works, and a single
empty --link clears the list. Both are read back through profile show
and the JSON API.
Storage is migration 0026: about, about_format, and a JSON links
column on users and orgs, all read and written through
store.Profile. auth import previously only restored a profile with a
description or website set, so a bundle carrying only the new fields
would have been dropped.
The web renders about between the profile header and the activity graph,
reusing renderReadme so org and markdown behave the same as they do for
a repository README. Links render as chips under the website line with
rel="nofollow me".
Profile editing stays SSH/CLI-only, as description and website already were.