dsh-file-drop: Writing Non-Image File Paths into the DSH Input Field

`dsh-file-drop` is a persistent plugin for DeepSeek Harness (DSH), designed to address the inefficiency of non-image files (such as PDF, Word, Excel, etc.) in DSH, which currently can only be handled through manual path copying. The plugin offers three file input methods: dragging and dropping files anywhere in the window, clicking the paperclip button for multi-selection, and hover bubble hints. It supports directly writing file paths into the input box draft for the agent to read. Its path acquisition strategy attempts in the following priority order: first, directly obtaining the original Finder path through the desktop shell (zero upload, no size limit); second, using the `text/uri-list` path from the drag-and-drop operation; finally, uploading files to the session workspace via the `POST /api/dsh-file-drop` endpoint (with a single-file limit of 25MB). The plug