test(transcript): cover coalesce created_at behavior

Lock in that coalescing streaming fragments carries the latest
created_at, and falls back to the previous timestamp when the merged
fragment has none.

Co-authored-by: multica-agent <github@multica.ai>

packages/views/common/task-transcript/build-timeline.test.ts

@@ -76,4 +76,29 @@ describe("task transcript timeline", () => {
     expect(items[0]?.content).not.toContain("abc123xyz");
     expect(items[0]?.content).not.toContain("def456");
   });
+
+  it("keeps the latest created_at when coalescing streaming fragments", () => {
+    const items = coalesceTimelineItems([
+      { seq: 1, type: "text", content: "hello ", created_at: "2026-06-09T09:00:00.000Z" },
+      { seq: 2, type: "text", content: "world", created_at: "2026-06-09T09:00:05.000Z" },
+    ]);
+
+    expect(items).toEqual([
+      expect.objectContaining({
+        seq: 1,
+        type: "text",
+        content: "hello world",
+        created_at: "2026-06-09T09:00:05.000Z",
+      }),
+    ]);
+  });
+
+  it("falls back to the previous created_at when the merged fragment has none", () => {
+    const items = coalesceTimelineItems([
+      { seq: 1, type: "text", content: "hello ", created_at: "2026-06-09T09:00:00.000Z" },
+      { seq: 2, type: "text", content: "world" },
+    ]);
+
+    expect(items[0]?.created_at).toBe("2026-06-09T09:00:00.000Z");
+  });
 });

server/internal/handler/daemon.go

@@ -2096,21 +2096,8 @@ func (h *Handler) ReportTaskMessages(w http.ResponseWriter, r *http.Request) {
 		}
 
 		if workspaceID != "" {
-			createdAt := ""
-			if created.CreatedAt.Valid {
-				createdAt = created.CreatedAt.Time.UTC().Format(time.RFC3339Nano)
-			}
-			h.publishTask(protocol.EventTaskMessage, workspaceID, "system", "", taskID, protocol.TaskMessagePayload{
-				TaskID:    taskID,
-				IssueID:   uuidToString(task.IssueID),
-				Seq:       msg.Seq,
-				Type:      msg.Type,
-				Tool:      msg.Tool,
-				Content:   msg.Content,
-				Input:     msg.Input,
-				Output:    msg.Output,
-				CreatedAt: createdAt,
-			})
+			h.publishTask(protocol.EventTaskMessage, workspaceID, "system", "", taskID,
+				taskMessageToPayload(created, taskID, uuidToString(task.IssueID)))
 		}
 	}