The environments surface: list, delete, and start a simulation.

An environment is the job that built it (the world itself lives in object storage, addressed from the job's metadata), so these endpoints project the same rows the harness-jobs API serves. They exist separately because the list needs a row, not a run: the jobs list returns every event, receipt and stage-output payload for up to a hundred jobs, which is a detail document repeated a hundred times.

Running and grading a simulation are deliberately not here. run starts one and returns 202; progress is read from the job.