dsh-cost-meter: DSH Session and Turn Cost Estimation Plugin

`dsh-cost-meter` is a DeepSeek Harness plugin for monitoring API costs at the session and turn level. It supports price synchronization with models.dev, OpenRouter, and DeepInfra, and provides dual-currency display in USD/CNY along with detailed cost breakdown statistics. It also supports advanced rules such as custom model unit prices, price-sync caching, and holiday calendars, helping developers manage development costs with greater precision. To install it, run `dsh plugin --profile web add -w @guojinpeng/dsh-cost-meter`. Ensure your DSH version is 0.2.0-rc.2 or higher.