新增: Reviewer仲裁+命令互斥锁+冲突解决IPC(批次C散项)

- coordinator: arbitrate_conflicts 方法(规则仲裁:成功方优先/双方成功推荐合并/都失败手动)

- coordinator: ConflictItem 加 subtask_a/subtask_b/recommendation 字段 + ConflictResolution 枚举

- command_lock.rs: CommandLockRegistry (dir+cmd首词 Semaphore 串行化,5个测试全绿)

- resolve_conflict IPC: 解决冲突→更新DB→emit AiConflictResolved 事件闭环

- 3个仲裁测试 + 5个互斥锁测试全绿

- 零编译警告

src-tauri/src/lib.rs

@@ -436,6 +436,8 @@ pub fn run() {
             // Plan 执行开关
             commands::settings::set_plan_execution,
             commands::settings::get_plan_execution,
+            // 冲突解决
+            commands::settings::resolve_conflict,
         ])
         .run(tauri::generate_context!())
         .expect("error while running tauri application");