fix: doc_query chronological insert, register cli/webui output channels

- context.go: add InsertByTimestamp for chronological context insertion
- toolcall.go: doc_query uses InsertByTimestamp instead of Append
- agent_tools_test.go: update tests to use payload/type keys
- cli/plugin.go: register output_send__cli channel
- webui/plugin.go: register output_send__webui channel

internal/agent/core/toolcall.go

@@ -503,7 +503,7 @@ func (a *Agent) executeDocTool(tc agentAPI.ToolCall) string {
 			if len(content) > 2000 {
 				content = content[:2000] + "..."
 			}
-			a.context.Append(ContextEvent{
+			a.context.InsertByTimestamp(ContextEvent{
 				Timestamp: d.CreatedAt,
 				Source:    "cold_storage",
 				Input:     fmt.Sprintf("加载文档记忆: %s", query),