新增: 多Agent数据层(V36迁移+3新表+Repo CRUD+7个测试全绿)

- V36: ai_plans/ai_subtasks/ai_conflicts 3 新表 + ai_messages/ai_tool_executions 加 subtask_id

- models: PlanRecord/SubTaskRecord/ConflictRecord 结构体

- PlanRepo/SubTaskRepo/ConflictRepo CRUD(insert/get/list_by_*/update_status/resolve)

- 7个 Repo 单元测试全部通过(内存 SQLite + 全迁移)

- 顺带修复 task_repo.rs 预存测试编译错误(trec_full 参数类型+缺失 await)

crates/df-storage/src/models.rs

@@ -497,3 +497,62 @@ pub struct ModuleDependencyRecord {
     pub label: Option<String>,
     pub created_at: String,
 }
+
+// ============================================================
+// 多 Agent 并行执行模型 (V36)
+// ============================================================
+
+/// Plan 记录(一次用户消息触发的并行执行计划)
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct PlanRecord {
+    pub id: String,
+    pub conversation_id: String,
+    /// 触发 Plan 的用户消息 id
+    pub user_message_id: Option<String>,
+    /// planning / executing / merging / done / error
+    pub status: String,
+    pub subtask_count: i64,
+    pub created_at: String,
+    pub completed_at: Option<String>,
+}
+
+/// SubTask 记录(Plan 拆解出的子任务)
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct SubTaskRecord {
+    pub id: String,
+    pub plan_id: String,
+    /// 分配的人设 id(coder/reviewer/architect/tester/analyst)
+    pub persona_id: Option<String>,
+    /// 子任务意图描述
+    pub intent: String,
+    /// pending / running / done / error
+    pub status: String,
+    /// DAG 层级(0 起)
+    pub layer: i64,
+    /// 依赖的 SubTask id 列表(JSON 数组字符串)
+    pub deps: Option<String>,
+    /// Git worktree 分支名(NULL=非 Git 工程降级串行)
+    pub branch: Option<String>,
+    pub created_at: String,
+    pub completed_at: Option<String>,
+}
+
+/// 冲突记录(合并时检测到的文件/语义冲突)
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct ConflictRecord {
+    pub id: String,
+    pub plan_id: String,
+    pub file_path: String,
+    /// file(同文件路径) / semantic(编译失败)
+    pub conflict_type: String,
+    pub subtask_a: Option<String>,
+    pub subtask_b: Option<String>,
+    pub diff_a: Option<String>,
+    pub diff_b: Option<String>,
+    /// pending / a / b / merged / manual
+    pub resolution: String,
+    /// reviewer / user
+    pub resolved_by: Option<String>,
+    pub created_at: String,
+    pub resolved_at: Option<String>,
+}