dsh-knj-scheduler: Scheduled Task Scheduler for DeepSeek Harness

`dsh-knj-scheduler` is a scheduled task scheduler plugin for DeepSeek Harness (DSH), designed to automate repetitive operations. It supports automatically starting prompt sessions or KNJ workflow tasks using cron expressions, specified times, or minute intervals. Core features include dual-tab management for task lists and execution records, working directory configuration, persistent storage, and execution status monitoring. Installation requires the dependencies `dsh-scheduler` and `dsh-knj-menu`. The plugin includes security validation, reentry prevention and concurrency control, and atomic write mechanisms to ensure reliable and secure task scheduling, helping users efficiently automate background task management.