dsh-cost-display: Display session cost in DSH status bar

`dsh-cost-display` is an open-source cost display plugin for DeepSeek Harness (DSH), designed to address the issue of unintuitive fee information during session debugging. The plugin displays the cumulative cost of the current session in real-time on the status bar, supporting hover to view token usage and Chain of Thought (CoT) statistics broken down by model. Its core features include support for automatic pricing based on Beijing time peak and off-peak hours, configurable effective dates to accommodate official price adjustments, automatic synchronization of the model list, and fallback pricing for unknown models (distinguished by a `?` prefix). Users can quickly install it via the `dsh` command or by manually modifying the configuration, and flexibly manage the price table, peak/off-peak windows, and toggles in the settings page. Cost estimation is based on multiplying input, cache, and output tokens by their respective unit prices; configuration changes take effect immediately for new requests, but historical data remains unchanged. It should be noted that this cost...