feat(workspace): stack hashtag back button above heading and add dedicated hashtag markdown note (#tag.md)

internal/domain/models.go

@@ -314,9 +314,11 @@ type TagDocumentGroup struct {
 }
 
 type TagDetails struct {
-	Tag          string             `json:"tag"`
-	Documents    []TagDocumentGroup `json:"documents"`
-	TotalMatches int                `json:"totalMatches"`
+	Tag           string             `json:"tag"`
+	NoteContent   string             `json:"noteContent"`
+	NoteUpdatedAt string             `json:"noteUpdatedAt,omitempty"`
+	Documents     []TagDocumentGroup `json:"documents"`
+	TotalMatches  int                `json:"totalMatches"`
 }
 
 type SpaceMember struct {