Design doc for issue #119: named per-user/shared save/load (chat + web),
auto-restore-and-resume of the live queue across restart (both behind an
admin-controlled savedQueuesEnabled flag, default off), and an independent
playKeepsQueue toggle so single-song !play inserts-and-plays instead of
clearing the queue. All toggles default off — no behavior change until opted in.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
