dsh-api-budget: API Latency Budget

`dsh-api-budget` is a pure Node.js plugin designed to address the difficulty of precisely calculating interface latency by parameters in DeepSeek Harness (DSH). It provides an `api_budget` tool that enables detailed latency budget calculations locally. The plugin requires no external network dependencies, is easy to install, is released under the MIT License, and is suitable for developers who need fine-grained control over calculation logic.