dsh-prompt-history-plugin: Shell-Style Prompt History Navigation

`dsh-prompt-history-plugin` is a DeepSeek Harness plugin maintained by hotpot-labs, designed to eliminate the hassle of repeatedly typing prompts through shell-style interaction. It does not render any UI; instead, it extends the behavior of the input box and allows quick recall of history entries using the up and down arrow keys. History data is automatically deduplicated and stored in the browser's `localStorage`, with a maximum of 100 entries retained. To use the plugin, ensure the cursor is at the beginning of the line; pressing ↑ the first time triggers history navigation, while pressing ↓ restores the current draft or exits navigation. The plugin does not interfere with IME input, runs entirely locally, and remains non-intrusive to the UI.