dsh-cost-tracker: Record daily LLM call costs for DeepSeek Harness Web

dsh-cost-tracker is an MIT-licensed DeepSeek Harness Web client plugin designed to address the issue of fragmented token usage data from model calls, which makes it difficult to review usage by dimensions. The plugin automatically records usage for every LLM call generated after installation, including input, cache hits, output, and reasoning tokens, and estimates costs based on a customizable pricing table (supporting peak-hour multipliers). It provides three entry points: a sidebar button, the session title bar, and beside the input box, supporting multi-dimensional cost viewing by overview, model, session, and recent calls. Users can modify price settings, and historical data will be recalculated accordingly. The plugin only calculates usage by reading the `usage` data from API responses locally; it does not trigger model calls, involves no network reporting, and does not store API keys. Data is saved locally; uninstalling the plugin will result in data deletion.