dsh-breathing: Breathing Exercises

`dsh-breathing` is a breathing exercise client plugin designed specifically for DeepSeek Harness (DSH). It is built with pure Node.js, works offline, and provides instant breathing suggestions by registering a `breathing` tool. It must be installed, and its dependencies met, before use. The plugin offers users a lightweight local tool for mental regulation, but the mental health content is for reference only and does not constitute professional medical advice.