Renaming checks for a name collision first (characters.char_name has
no unique constraint in the schema, so this has to be enforced at the
application level to avoid two characters silently sharing a name),
and also updates list_friend.namefriend for any rows referencing this
character's id -- that column is a denormalized display-name cache in
other players' friend lists and would otherwise go stale on rename.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
