prompt-optimizer-plugin: Optimizing the DSH Input Box Draft

`prompt-optimizer-plugin` is a DeepSeek Harness (DSH) plugin designed to optimize vague user prompts. After users draft their prompt and click "✨ Optimize", the plugin leverages session context (such as recent conversations and topics) to automatically rewrite and populate the input field, with support for undo and privacy protection. Installation requires running a specified command via pnpm, and all configuration and privacy data are stored locally.