DeepSeek Harness Plugin: dsh-dual-checkin

`dsh-dual-checkin` is a plugin for DeepSeek Harness (DSH) designed to automate check-ins and status monitoring across the Trae, WorkBuddy, and Qoder platforms. Leveraging a parallel architecture, it performs seamless check-ins by reading local login states and provides a full-width sidebar panel to display platform statuses, points, and expiration reminders. Configuration supports PAT tokens or the DSH credential service, with data security strictly adhering to the "local read-only" principle. It can be installed via CLI, Web UI, or local cloning; once installed, it automatically starts with the DSH process and ensures idempotency and non-blocking execution.