Submit a sweep: one build, N variants

Submit a sweep: N variants of one job in a single call (1-256). shared carries everything submit_job accepts; each entry of variants overrides command, env, or build_args for its job (overrides replace the shared field wholesale). Put variant parameters in env: env and command are not in the build key, so an env/command-only sweep is ONE image build + N runs; overriding build_args builds a separate image per distinct combination. Every variant becomes an ordinary job - same validation, fairness, and billing as submit_job - sharing label, so list_jobs(label, summary: true) is the one-call rollup and each job's $GMN_RESULT_PATH verdict comes back in it. Validation is all-or-nothing: any invalid variant rejects the whole batch with the offenders named, and nothing is submitted. Variant i derives idempotency key "{key}:{i}", so resubmitting the same batch returns the same jobs. Cancel losers individually with cancel_job. Pass shared.depends_on: {job, require} to gate the WHOLE sweep on one earlier job's declared result: no variant builds, queues or places until it succeeds and the predicate holds, so one cheap probe can decide whether 256 expensive variants ever cost anything. Pass shared.output_to: {connection, dest} to land every variant's output under one connection prefix - each at <dest><job_id>-<attempt>.tar, so a 256-shard generation sweep becomes one dataset in your own bucket with no key collisions and no credential in any container. SIZING: a sweep of many SHORT variants (minutes each) of one image is usually a TASK SET wearing sweep clothes - submit_job's tasks parameter runs the same units under ONE container start with per-unit retries and autoscaled runners; keep the sweep for variants that differ by build or run long.