dsh-shanhai-stats: DeepSeek Harness Usage Stats Plugin

The `dsh-shanhai-stats` plugin for DeepSeek Harness (DSH) is used to collect and display DSH session usage. It extracts data from logs and provides total summaries, daily trends, a GitHub-style heatmap, and details grouped by model/provider. It supports historical backfilling, resumable scanning, and subagent statistics. The plugin includes four views: a total badge, a daily line chart, a heatmap, and a usage details table. When enabled, it scans local history, with data metrics consistent with DSH.