Concept-Check: Extraction

You have installed two seams this arc: the Source / Transform / Sink traits, and the Extract / Transform / Load split, with the CelesTrak source and the JSONL sink as the first concrete implementations. This check pins down the parts that are easy to get almost right — the TLE checksum arithmetic, why Row carries a tag, which stage owns parsing, and the object-safety property that lets the orchestrator schedule a dyn Source later.

Two of these are Tracing questions: read the program, decide whether it compiles, and if it does, predict its exact output before revealing the answer. Predicting is the point.