dsh-image-picker: Attachment Picker Plugin for DeepSeek Harness Web GUI

The `dsh-image-picker` plugin adds a file selection entry to the left of the input box, addressing the difficulties of adding non-image files and limits on path retrieval in the DeepSeek Harness Web environment. Maintained by `liujia-io`, it supports processing images and text files (.txt, .md, .docx). Images are injected directly into the official pipeline, while text files are read by the browser and temporarily stored on the local server, requiring the Agent to read them through tools. The plugin enforces a 25MB per-file size limit and includes filename sanitization and fault-tolerant fallback mechanisms. Installation command: `dsh plugin --profile web add github:liujia-io/dsh-image-picker`.