luxueliu-usage-command: DSH local machine API cost command

`luxueliu-usage-command` is an MIT-licensed DeepSeek Harness plugin designed to address the challenges of cost accounting when invoking models from multiple sources. By reading the local LiteLLM gateway's billing file `gateway_usage.jsonl`, it provides a `/usage` command to display a daily cost report categorized by model and hour. The plugin's core features include supporting pricing for three categories of models—official direct connections, resellers, and package pools; automatically adapting currency based on the user's time zone (e.g., Chinese users see RMB and Beijing Time); supporting fine-grained pricing based on cache hit status; and allowing the extension of custom model prices and alias mappings via a configuration file. Usage requires a Node.js 22.18+ environment, and DSH must be restarted after installation to be effective.