feat(tasks): deepening a task into a note keeps the task, linked to the note's first checkbox

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/storage/thoughts.go

@@ -310,6 +310,7 @@ func (s *Store) UpdateThoughtTriage(userID, thoughtID, action, convertTo, target
 			newStatus = domain.StatusConverted
 			convertedType = "task"
 		} else if convertTo == "document" {
+			isTask := thought.Status == domain.StatusKept || (thought.Status == domain.StatusConverted && thought.ConvertedType == "task")
 			newStatus = domain.StatusConverted
 			convertedType = "document"
 			title := thought.Content
@@ -373,6 +374,13 @@ func (s *Store) UpdateThoughtTriage(userID, thoughtID, action, convertTo, target
 			doc, err := s.CreateDocument(userID, "", title, "📄", "", blocks, thought.Tags, false)
 			if err == nil && doc != nil {
 				convertedRefID = doc.ID
+				// A task stays in its list and becomes the note's first checkbox (same link as a task made
+				// from a note block); a thought from the inbox turns into the note
+				if isTask {
+					newStatus = domain.StatusKept
+					convertedType = "document_block"
+					convertedRefID = doc.ID + ":" + blocks[0].ID
+				}
 			}
 		} else if convertTo == "list_item" && targetListID != "" {
 			// Same rule as adding an item in the list itself: owner or editor