dsh-bill: Cost Attribution and Usage Dashboards for DSH

`dsh-bill` is a DSH cost attribution and usage dashboard plugin designed to break down session expenses from a simple total into specific content types, such as model output, tool input, system prompts, and user input. Maintained by Jannchie and built on `llm-pricing` for price parsing, its core features include: splitting bills by content type with trend charts and heatmaps; displaying the cost, step count, and cache hit rate for each conversation round; providing a persistent interface status, such as a sidebar showing today's spending versus budget; generating detailed reports covering totals, monthly forecasts, and account balance; supporting daily, monthly, and full-cycle budget settings with overspend alerts; integrating real-time exchange rates for approximately 166 currencies; and offering a `bill_stats` tool that allows the model to directly query spending data. Installation requires the `dsh plugin --p