Version: 0.8.9.dev.260405

后端：
1.新建 tools/state.go：定义 ScheduleState/ScheduleTask/TaskSlot 等工具层状态类型，含 DayToWeekDay/TaskByStateID/Clone 等辅助方法
2.新建 conv/schedule_state.go：实现 DB 模型→ScheduleState 的转换函数（LoadScheduleState）和状态对比 diff 函数（DiffScheduleState），含 Section 压缩/解压和嵌入关系解析
3.新建 tools/read_helpers.go：读工具公共辅助函数（格式化、占用统计、空闲区间计算、可嵌入查询）
4.新建 tools/read_tools.go：实现5个读工具（GetOverview/QueryRange/FindFree/ListTasks/GetTaskInfo），返回自然语言+轻结构，19个单元测试全部通过
5.更新 AGENTS.md 第13条：明确要求可验证代码必须跑单测，跑完删除测试文件
前端：无
仓库：无

backend/newAgent/tools/state.go

@@ -0,0 +1,117 @@
+package newagenttools
+
+// DayMapping maps a day_index to a real (week, day_of_week) coordinate.
+type DayMapping struct {
+	DayIndex  int `json:"day_index"`
+	Week      int `json:"week"`
+	DayOfWeek int `json:"day_of_week"`
+}
+
+// ScheduleWindow defines the planning window.
+type ScheduleWindow struct {
+	TotalDays  int          `json:"total_days"`
+	DayMapping []DayMapping `json:"day_mapping"`
+}
+
+// TaskSlot is a compressed time slot using day_index and section range.
+type TaskSlot struct {
+	Day       int `json:"day"`
+	SlotStart int `json:"slot_start"`
+	SlotEnd   int `json:"slot_end"`
+}
+
+// ScheduleTask is a unified task representation in the tool state.
+// It merges existing schedules (from schedule_events) and pending tasks (from task_items)
+// into one flat list that the tool layer operates on.
+type ScheduleTask struct {
+	StateID  int    `json:"state_id"`
+	Source   string `json:"source"`    // "event" | "task_item"
+	SourceID int    `json:"source_id"` // ScheduleEvent.ID or TaskClassItem.ID
+	Name     string `json:"name"`
+	Category string `json:"category"` // e.g. "课程", "学习", "作业"
+	Status   string `json:"status"`   // "existing" | "pending"
+	Locked   bool   `json:"locked"`
+
+	// Existing task: compressed slot ranges. Pending task: nil until placed.
+	Slots []TaskSlot `json:"slots,omitempty"`
+	// Pending task: required consecutive slot count.
+	Duration int `json:"duration,omitempty"`
+	// source=task_item only: TaskClass.ID for category lookup.
+	CategoryID int `json:"category_id,omitempty"`
+	// source=event only: whether this slot allows embedding other tasks.
+	CanEmbed bool `json:"can_embed,omitempty"`
+
+	// Embed relationships (resolved after all tasks are loaded).
+	EmbeddedBy *int `json:"embedded_by,omitempty"` // host: which state_id is embedded into me
+	EmbedHost  *int `json:"embed_host,omitempty"`  // guest: which state_id's slot I'm embedded into
+
+	// Internal: not exposed to LLM, used for flush/diff logic.
+	EventType string `json:"event_type,omitempty"` // "course" | "task" (source=event only)
+}
+
+// ScheduleState is the full tool operation state.
+type ScheduleState struct {
+	Window ScheduleWindow `json:"window"`
+	Tasks  []ScheduleTask `json:"tasks"`
+}
+
+// DayToWeekDay converts day_index to (week, day_of_week).
+func (s *ScheduleState) DayToWeekDay(day int) (week, dayOfWeek int, ok bool) {
+	for _, m := range s.Window.DayMapping {
+		if m.DayIndex == day {
+			return m.Week, m.DayOfWeek, true
+		}
+	}
+	return 0, 0, false
+}
+
+// WeekDayToDay converts (week, day_of_week) to day_index.
+func (s *ScheduleState) WeekDayToDay(week, dayOfWeek int) (day int, ok bool) {
+	for _, m := range s.Window.DayMapping {
+		if m.Week == week && m.DayOfWeek == dayOfWeek {
+			return m.DayIndex, true
+		}
+	}
+	return 0, false
+}
+
+// TaskByStateID finds a task by state_id. Returns nil if not found.
+func (s *ScheduleState) TaskByStateID(stateID int) *ScheduleTask {
+	for i := range s.Tasks {
+		if s.Tasks[i].StateID == stateID {
+			return &s.Tasks[i]
+		}
+	}
+	return nil
+}
+
+// Clone returns a deep copy of the ScheduleState.
+func (s *ScheduleState) Clone() *ScheduleState {
+	if s == nil {
+		return nil
+	}
+	clone := &ScheduleState{
+		Window: ScheduleWindow{
+			TotalDays:  s.Window.TotalDays,
+			DayMapping: make([]DayMapping, len(s.Window.DayMapping)),
+		},
+		Tasks: make([]ScheduleTask, len(s.Tasks)),
+	}
+	copy(clone.Window.DayMapping, s.Window.DayMapping)
+	for i, t := range s.Tasks {
+		clone.Tasks[i] = t
+		if t.Slots != nil {
+			clone.Tasks[i].Slots = make([]TaskSlot, len(t.Slots))
+			copy(clone.Tasks[i].Slots, t.Slots)
+		}
+		if t.EmbeddedBy != nil {
+			v := *t.EmbeddedBy
+			clone.Tasks[i].EmbeddedBy = &v
+		}
+		if t.EmbedHost != nil {
+			v := *t.EmbedHost
+			clone.Tasks[i].EmbedHost = &v
+		}
+	}
+	return clone
+}