feat: room scoping (org/DM/other sections), unread badge on nav, highlight.js CSS

src/lib/stores/matrix.ts

@@ -288,6 +288,13 @@ export const roomSummaries = derived(rooms, ($rooms): RoomSummary[] => {
   return summaries;
 });
 
+/**
+ * Total unread count across all rooms (for nav badge)
+ */
+export const totalUnreadCount = derived(roomSummaries, ($summaries): number => {
+  return $summaries.reduce((sum, room) => sum + (room.isSpace ? 0 : room.unreadCount), 0);
+});
+
 // ============================================================================
 // Messages
 // ============================================================================