- Read states store: smarter hasUnread compares against latest message
- ConversationList: orange dot + bold name for unread DMs
- DMChat: auto-mark-read when viewing conversation
- WS handler: mark DM read on new message while active+focused
ConversationList was only setting activeConversationId in the store
but never navigating. If the Outlet was still showing ChatArea from
a server channel route, DMChat never mounted. Now every click
navigates to /dm/:conversationId so the router mounts DMChat.