dsh-preview: A Front-End Self-Check Tool for DeepSeek Harness

`dsh-preview` is a workflow plugin for DeepSeek Harness (DSH) that addresses the issue of agents determining task completion solely based on code while ignoring actual rendering outcomes. The plugin provides headless browser tools and a `frontend-verify` self-check skill, requiring agents to perform a complete closed-loop verification process: opening pages, checking the console, reading layout information, running interaction tests, and recording screenshots. Core features include six browser tools and an automated verification loop, ensuring that agents detect and fix errors before declaring a task complete. The plugin supports multiple browsers and includes a secure access-control mechanism that requires explicit authorization for external hosts. Through this rigorous verification discipline, `dsh-preview` transforms frontend acceptance from a manual task into a built-in agent capability, reducing the need for human intervention.