[6/6][misc] feat: container lifecycle benchmark for harbor rollouts

[mathewjhan]

Part of splitting #272 into reviewable pieces (6/6). Exercises everything below it in the stack.

What this adds

A CLI that measures how long the full rollout lifecycle takes on the Harbor backend: submit, container build/start, agent run, verification, teardown. It reports cold and warm timings separately and per-rollout p50/p95/max, which is how regressions in container startup cost were found and fixed during development.

It runs against the bundled bench_harness project by default (a minimal workflow + grader), or against any Harbor task folder via --tasks-dir. Rollout ids carry a per-invocation nonce so concurrent bench runs cannot collide.

Example

# default bench task, 3 runs of 5 concurrent rollouts
uv run benchmarks/container_lifecycle/container_lifecycle_bench.py --runs 3 --concurrency 5

# against a real dataset task, without baking the SDK into the image
uv run benchmarks/container_lifecycle/container_lifecycle_bench.py \
    --tasks-dir harbor-datasets/datasets/algotune/algotune-aes-gcm-encryption \
    --runs 3 --concurrency 5 --no-patch-dockerfile-with-sdk

Output shows per-run wall time, success counts, rollouts/sec, and warm-run latency percentiles.