dsh--to-rust: JSON to Rust Structs

DSH (DeepSeek Harness) is a plugin-based ecosystem. The `dsh--to-rust` plugin provides developers with a convenient way to convert JSON into Rust structs. Implemented in Node.js, it generates code compatible with the `serde` library. After installing it using `dsh plugin add`, it must be enabled in the profile configuration. To use it, call the `json_to_rust` tool in a session to perform the conversion. Developers should review the source code and license themselves.