Voice channels rendered with VoiceChannel component have no text reading/acking
UI, so messages in them created phantom unread indicators on the space sidebar
that users could never clear. Root cause was a message in the counter-strike
voice channel with no read state.
Three-layer fix:
- spaceStore: track voiceChannelIds set, exclude voice channels from
channelLastMessageIds so setReadStates never marks them unread
- useWebSocket: skip markChannelUnread for voice channels on message_created,
prune orphaned unreads on every ready event
- chatStore: validate preserved unreads against channelToSpaceMap to drop
orphans that don't map to any known channel