failoverDmOriginsFromDisconnected(origin) walks pinned DMs and re-keys
them to a connected sibling origin's local channel id (via dmAlternatives
federatedId lookup). Preference: home first, then any connected remote in
insertion order. rekeyDmChannel performs the atomic rename across
spaceStore (dmChannels / channelOriginMap / channelLastMessageIds /
dmAlternatives), chatStore (via rekeyChannelState), and the URL (via
history.replaceState when viewing the rekeyed DM). Voice state is
intentionally untouched — LiveKit sessions can't migrate across origins.
Old origin's local id is retained in dmAlternatives for possible later
fail-back without another ready round-trip.
Jannis Braun
d393a870c2