dsh-phone-et: Phone Etiquette Plan Generation Tool

The `dsh-phone-et` plugin provided by DeepSeek Harness (DSH) is specifically designed for telephone communication etiquette scenarios. It is implemented in pure Node.js with no network dependencies and returns appropriate etiquette guidance based on parameters via the `phone_et` tool. Installation requires the `@deepseek-ai/cordis` and `@deepseek-ai/dsh-tools` dependencies, and once enabled, it can be invoked in a session. The plugin is maintained by uckkk.