feat(agent): 经验记忆 - 按任务相关度排序召回，并过期清理待批准记忆

召回按主题、情境和中文双字命中加权；30天未处理的待批准记忆会在记录和压缩调度时过期，成功计数写入运行态以免事件窗口截断后误拦。

backend/internal/app/cloud_agent_runtime.go

@@ -169,9 +169,11 @@ type cloudAgentRuntime struct {
 	// PiAssistantResponses counts successful assistant message_end events from
 	// the Pi runtime. Completion must not be inferred from a clean Node exit:
 	// a provider/session error can otherwise be reported as a successful run.
-	PiAssistantResponses int    `json:"piAssistantResponses,omitempty"`
-	IsGenerating         bool   `json:"isGenerating,omitempty"`
-	LastError            string `json:"lastError,omitempty"`
+	PiAssistantResponses        int    `json:"piAssistantResponses,omitempty"`
+	LessonEligibleToolSuccesses int    `json:"lessonEligibleToolSuccesses,omitempty"`
+	RememberLessonSuccesses     int    `json:"rememberLessonSuccesses,omitempty"`
+	IsGenerating                bool   `json:"isGenerating,omitempty"`
+	LastError                   string `json:"lastError,omitempty"`
 	// EmptyOutputEscalated 记录"空输出已经升级重试过几次"（关思考 + 放大输出预算）。
 	EmptyOutputEscalated int `json:"emptyOutputEscalated,omitempty"`
 	// StepTimeoutEscalated 记录"单步墙钟到点后已经关思考重试过几次"。