fix: clean up Docker verifier containers after runs

[DeSitterUniverse]

Summary

Clean up BenchLocal-owned Docker verifier containers when the final run lease is released. This is done to reduce RAM and resource usage from containers that are no longer needed when benchmarking.

Covered paths:

• full Bench Pack runs;
• scenario retries;
• run resumes;
• verifier/host setup failures;
• aborts and other run errors.

Implementation

• Centralize prepared-resource, host-resource, and verifier cleanup in one finalizer.
• Track active leases per Bench Pack so shared verifier containers stay alive while another run/retry/resume is using them.
• Make lease release idempotent.
• Treat cleanup as best-effort: a failed cleanup is logged and cannot replace the original run/setup error.
• Remove containers only. Images, model files, run artifacts, and logs are preserved.
• Existing explicit verifier start/stop/status APIs are unchanged.

Why

A verifier container is a short-lived benchmark dependency, but it previously remained running after a run completed. This retains Docker/Node process memory until manually stopped.

Measured local impact:

Workload	Verifier memory while active	Potential reclaim after cleanup
StructOutput-15, full 15-scenario model run	12.13 MiB peak	~10–12 MiB
CLI-40 live integration sample	18.59 MiB	~18.59 MiB
Three verifier containers held live	46.96 MiB aggregate	~46.96 MiB

The StructOutput-15 measurement used 1,014 Docker memory samples during a 33m44s run. The container peaked at 12.13 MiB, then no container remained after finalization. Potential memory savings are higher than tested.

Validation

• npm.cmd run build:compile — passed.
• npm.cmd test — passed after the documented compile step.
• git diff --check — passed.
• Normal run — verifier removed.
• Abort after container startup — expected abort returned; verifier removed.
• Concurrent same-pack runs — verifier stayed available until the final lease released, then was removed.
• Setup-failure cleanup — covered by the same finalization path.