The notification filter accepted any note whose `inGatherers` contained
a MarmotGroupChatroom, regardless of which account's list that chatroom
belonged to. Since notes live in the global LocalCache and accumulate
gatherer references across account switches (and are not cleaned up on
leave), old messages stayed in Notifications after switching accounts
or leaving a group.
Mirror the NIP-17 DM guarantee: only accept a Marmot message when the
gatherer is the same instance currently held by the active account's
`marmotGroupList.rooms[nostrGroupId]`.
Claude
79188e3f7f