dsh-token-monitor: DSH Sidebar Token Usage Plugin

`zhangzheng25/dsh-token-monitor` is a DeepSeek Harness (DSH) plugin designed to provide intuitive token usage monitoring. It adheres to the DSH "everything is a plugin" philosophy, displaying a "Today's Usage" card at the bottom of the sidebar. Clicking it opens a statistics window showing token totals for today, the last 7 days, and the last 30 days, along with stacked usage charts by model, model rankings, and session statistics. The plugin auto-refreshes every 30 seconds, supports idempotent historical backfill to include pre-installation usage in statistics, and persists data bucketed by day for 181 days. Installation requires Node.js >=20 and can be done via the `dsh plugin add` command from GitHub or a local directory, with the plugin taking effect after restarting DSH. The project采