Reconstruct a JSON pipeline object that exists in ChRIS

Performing a GET on a pipeline should ideally return a JSON object analogous to the original pipeline JSON

Start by locating the GET pipeline command in the Rust ChRIS CLI and comparing its current response with the original pipeline JSON exposed by ChRIS. Done means a GET on a pipeline reconstructs and returns an analogous JSON object; the issue names no files or tests, so the relevant entry point and verification steps must first be identified.

Written by the indexing model from the issue text.