Persist subagent intermediate messages for the agent tracker view.

internal/runmgr/runmgr.go

@@ -488,6 +488,14 @@ func (m *Manager) spawnSubagent(parentCtx context.Context, parent core.Run, name
 	m.st.UpdateRun(&child)
 	m.emit(child.ConversationID, child.ID, core.EvAgentResult, payload)
 
+	// 子代理中间过程落库（AgentTracker 弹窗的权威数据源；消息树带 run_id 归属）。
+	m.mu.Lock()
+	subParts := append([]core.Part{}, h.assistant...)
+	m.mu.Unlock()
+	if len(subParts) > 0 {
+		_ = m.st.AppendMessage(&core.Message{ConversationID: child.ConversationID, RunID: child.ID, Role: core.RoleAssistant, Parts: subParts})
+	}
+
 	m.mu.Lock()
 	delete(m.active, child.ID)
 	m.mu.Unlock()