feat: unread indicator (*) for rooms with new messages

Rooms that receive a message while not active show a * prefix in the
sidebar. The marker clears when you tab to that room.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

cmd/tui/main.go

@@ -107,6 +107,7 @@ type model struct {
 	rooms      []string // "general" always first; DM rooms appended
 	activeRoom int
 	messages   map[string][]entry
+	unread     map[string]bool // rooms with messages since last viewed
 
 	peers     map[proto.PeerID]string // connected peers: id → alias
 	peerOrder []proto.PeerID
@@ -131,6 +132,7 @@ func newModel(ipcPort int, network string) model {
 		networkName: network,
 		rooms:       []string{"general"},
 		messages:    make(map[string][]entry),
+		unread:      make(map[string]bool),
 		peers:       make(map[proto.PeerID]string),
 		input:       ti,
 		status:      "connecting…",
@@ -215,9 +217,11 @@ func (m model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
 			m, cmds = m.doSend(cmds)
 		case msg.Type == tea.KeyTab:
 			m.activeRoom = (m.activeRoom + 1) % len(m.rooms)
+			delete(m.unread, m.activeRoomName())
 			m = m.refreshViewport()
 		case msg.Type == tea.KeyShiftTab:
 			m.activeRoom = (m.activeRoom - 1 + len(m.rooms)) % len(m.rooms)
+			delete(m.unread, m.activeRoomName())
 			m = m.refreshViewport()
 		default:
 			var tiCmd tea.Cmd
@@ -303,6 +307,9 @@ func (m model) applyEvent(evt proto.IpcMessage) model {
 			}
 			m.messages[msg.Room] = append(m.messages[msg.Room], e)
 			m = m.addRoom(msg.Room)
+			if msg.Room != m.activeRoomName() {
+				m.unread[msg.Room] = true
+			}
 			m = m.refreshViewport()
 		}
 	}
@@ -483,7 +490,11 @@ func (m model) renderRooms(boxH int) string {
 		if i == m.activeRoom {
 			lines = append(lines, styleActive.Width(innerW).Render("▶ "+label))
 		} else {
-			lines = append(lines, styleRoom.Width(innerW).Render("  "+label))
+			prefix := "  "
+			if m.unread[room] {
+				prefix = "* "
+			}
+			lines = append(lines, styleRoom.Width(innerW).Render(prefix+label))
 		}
 	}
 	for len(lines) < contentH {