DeepSeek Harness (DSH) Sidebar Plugin: Real-Time Display of Volcano Ark Agent Plan Usage

The DeepSeek Harness (DSH) plugin `dsh-ark-plan-usage` adds a visual card to the bottom of the Web UI sidebar, displaying real-time Agent Plan usage. The plugin retrieves data by calling the local `arkcli` and supports expand/collapse, color-coded warnings, and one-click re-login. With zero build, zero runtime dependencies, and a caching mechanism, it eliminates the need for developers to repeatedly switch to the terminal to check quotas.