dsh-show-picture: Enabling Agents to Display Images Directly in Conversations

The `dsh-show-picture` plugin is designed specifically for DSH Agent to address the issue of fragmented image display. It provides the `show_picture` tool, which renders image cards for local files and remote URLs directly in the chat stream. The plugin requires no additional file server: local files are transmitted as Base64 (up to 10 MiB), while remote URLs are loaded via HTML tags. It must be configured as a global static plugin during installation and takes effect automatically after a restart. When using it, specify the `path` parameter (for local files) or the `url` parameter (for remote URLs), and an `alt` description can be added. This plugin greatly improves the Agent's experience when presenting visual information.