docs(changelog): order every entry Added, Fixed, Changed

House rule from the operator: additions lead, fixes follow, behavior
changes close, and any other section (Removed, Security, the odd
Known-gaps note) keeps its relative order after those. Sections moved
whole; the sorted line-multiset of the file is byte-identical before
and after, so no bullet changed.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>