dsh-rich-artifacts: A DSH plugin to publish workspace files as chat Artifacts

dsh-rich-artifacts is a DSH plugin developed by Inkotake (MIT licensed) designed to solve the inconvenience of users having to manually view files on the host machine after an agent delivers them. It publishes workspace files as chat Artifacts: the model can render PNG/JPEG/WebP/GIFs inline in the conversation by calling the `publish_artifact` tool (with parameters including path, title, and display mode), while other files are generated as cards with a download button. Files are stored in an ArtifactStore based on SHA-256 content addressing, with metadata stored in `~/.dsh/artifacts/v1/`. Persistent session events only record metadata without storing the file body, ensuring files remain accessible correctly after reloading or forking historical sessions.