dsh-ui-cost: Real-Time Token Usage and Cost Estimation Plugin for DeepSeek Harness Web UI

The DeepSeek Harness (DSH) Web UI plugin `dsh-ui-cost` provides real-time token usage statistics and cost estimates. As a standalone plugin independent of the core code, it intercepts the stats row data to display turn information, performance metrics, cache status, and detailed billing information. Cost calculations follow the official pricing model and automatically switch between peak and off-peak rates. The plugin can be installed via the command line and automatically falls back to the default stats bar if uninstalled or if it crashes.