fix(sync): eliminate zombie focus, flush debounced state on window blur, remove stale closures and buffer ws messages

internal/ws/docroom.go

@@ -320,8 +320,10 @@ func (r *DocRoom) HandleEvent(evt DocSyncEvent, sender *DocWSClient) {
 			targetID = evt.Block.ID
 		}
 		if targetID != "" {
+			found := false
 			for i := range r.blocks {
 				if r.blocks[i].ID == targetID {
+					found = true
 					if evt.Block != nil {
 						r.blocks[i].Content = evt.Block.Content
 						r.blocks[i].Level = evt.Block.Level
@@ -359,6 +361,22 @@ func (r *DocRoom) HandleEvent(evt DocSyncEvent, sender *DocWSClient) {
 					break
 				}
 			}
+			if !found && evt.Block != nil {
+				newBlock := *evt.Block
+				newBlock.DocumentID = r.docID
+				if newBlock.Type == "" {
+					newBlock.Type = "text"
+				}
+				if newBlock.Level < 0 {
+					newBlock.Level = 0
+				}
+				r.blocks = append(r.blocks, newBlock)
+				r.blocks = normalizeRoomBlocks(r.docID, r.blocks)
+				bCopy := newBlock
+				evt.Block = &bCopy
+				evt.BlockID = targetID
+				mutated = true
+			}
 		}
 
 	case "block_deleted":
@@ -441,6 +459,11 @@ func (r *DocRoom) HandleEvent(evt DocSyncEvent, sender *DocWSClient) {
 			select {
 			case client.send <- msgBytes:
 			default:
+				slog.Warn("Doc room WS client send buffer full, dropping message",
+					"doc_id", r.docID,
+					"client_id", client.clientID,
+					"user_id", client.userID,
+				)
 			}
 		}
 	}