dsh-agnes-media: Agnes AI Image and Video Generation Plugin

The `dsh-agnes-media` plugin integrates Agnes's media generation capabilities into DeepSeek Harness (DSH) through the `agnes_image` and `agnes_video` tools. It supports text-to-image, image-to-image, text-to-video, and keyframe generation, with generated files saved by default to the local workspace. Configuration requires managing the API key via environment variables and setting the model name. It provides robust error handling (such as retry mechanisms) and asynchronous video task polling, addressing DSH's inability to handle non-conversational media requests and offering reliable support for multimodal agents.