refactor(project): issue Update tracks changed fields and skips no-op audit

internal/project/issue_service.go

@@ -128,24 +128,26 @@ func (s *issueService) Update(ctx context.Context, c Caller, slug string, number
 	}
 
 	title, desc := cur.Title, cur.Description
-	if in.Title != nil {
+	changed := map[string]any{}
+	if in.Title != nil && *in.Title != cur.Title {
 		title = *in.Title
+		changed["title"] = "<changed>"
 	}
-	if in.Description != nil {
+	if in.Description != nil && *in.Description != cur.Description {
 		desc = *in.Description
+		changed["description"] = "<changed>"
 	}
 
 	// requirement 三态：未传（in.RequirementNumber == nil）→ 保持
 	//                 传 nil 指针（**nil）→ detach
 	//                 传值（*RequirementNumber 不是 nil）→ resolve & validate
 	reqID := cur.RequirementID
-	auditFrom := ""
-	auditTo := ""
 	if in.RequirementNumber != nil {
-		auditFrom = "<unchanged>"
+		auditFrom := "<none>"
 		if cur.RequirementID != nil {
 			auditFrom = cur.RequirementID.String()
 		}
+		var auditTo string
 		if *in.RequirementNumber == nil {
 			reqID = nil
 			auditTo = "<none>"
@@ -157,18 +159,21 @@ func (s *issueService) Update(ctx context.Context, c Caller, slug string, number
 			reqID = &r.ID
 			auditTo = r.ID.String()
 		}
+		if auditFrom != auditTo {
+			changed["from_requirement"] = auditFrom
+			changed["to_requirement"] = auditTo
+		}
+	}
+
+	if len(changed) == 0 {
+		return cur, nil
 	}
 
 	out, err := s.repo.UpdateIssueCore(ctx, cur.ID, title, desc, reqID)
 	if err != nil {
 		return nil, err
 	}
-	meta := map[string]any{"changed_fields": "<various>"}
+	s.recordAudit(ctx, c, "issue.update", out.ID.String(), map[string]any{"changed_fields": changed})
-	if auditFrom != "" {
-		meta["from_requirement"] = auditFrom
-		meta["to_requirement"] = auditTo
-	}
-	s.recordAudit(ctx, c, "issue.update", out.ID.String(), meta)
 	return out, nil
 }