xby-bazi: Bazi Calculator Plugin

In DeepSeek Harness (DSH), developers can install the `xby-skill/xby-bazi` plugin via the command line to integrate BaZi charting and Chinese almanac lookup functionality. The plugin uses AI-powered calculations and requires registering on the official Xiaobenyang website to obtain an API key, which must be set with the `set_xby_apikey` command before use. Core functions include: setting the API key, retrieving BaZi details (requiring a specified Gregorian or lunar date/time and gender), retrieving a list of Gregorian dates/times based on the BaZi, and retrieving almanac information for a specified time (defaulting to today). Note that mutually exclusive parameter validation must be observed during use.