dsh-composer-resize: DSH Web Input Box Drag-to-Resize Plugin

The fixed height of the input box on the DeepSeek Harness (DSH) web interface causes long drafts to be clipped when the window is shrunk. The `dsh-composer-resize` plugin resolves this issue by adding a drag handle at the top. It supports up/down dragging to adjust the height, ranging from 52px to 75% of the viewport height. During dragging, the view remains anchored to the bottom of the text, ensuring the last few lines stay visible. The plugin is implemented entirely in the browser, does not invoke models or execute host commands, and depends on the DSH 0.1.0-rc.6 Web UI. Installation requires running the `dsh plugin` command and reloading the web page.