dsh-plugin-show-image: In-Session Image Rendering Plugin for DeepSeek Harness

The DeepSeek Harness (DSH) plugin `dsh-plugin-show-image` is designed to address the problem of bloated logs caused by transferring local images in LLM conversations. The plugin streams image bytes on demand via HTTP routing, supports inline rendering within the conversation flow and click-to-enlarge viewing, while keeping the data out of session logs. It features zero dependencies, security guards (8 MB limit and whitelist), and full reversibility. It is supported only in the `dsh web` environment; after installation, Agents can use the `show_image` tool to display local images.