Allow user to pass steps to resume command

[aliroberts]

Summary

• New -n, --steps N flag on weco resume. Runs N more evaluations from the last node by resetting the backend run's budget to `last_step

• N`.

• weco resume now accepts runs in the completed status when --steps is provided (previously only error / terminated were
  resumable).
• The resume confirmation prompt now shows the budget delta when --steps is set, and warns in yellow when the value would shrink the original budget.
• The progress UI picks up the new total from the resume response so the bar reflects the bumped target instead of the stale original.
• Omitting --steps keeps existing behavior 1:1 — weco resume <id> on a terminated/errored run still resumes to the original budget.

Files

• weco/cli.py — adds -n/--steps to configure_resume_parser; execute_resume_command threads it as additional_steps into resume_optimization.

  • weco/optimizer.py — resume_optimization accepts additional_steps; loosens the status gate to allow completed when set; passes steps through to the backend; refreshes total_steps from the resume response; new confirmation block with budget delta + shrink warning.
  • weco/api.py — resume_optimization_run forwards steps.
  • weco/core/api.py — WecoClient.resume_run accepts and forwards steps in the POST body.

  Semantics

  --steps N always means "N more evaluations from the last node" — uniform across error, terminated, and completed. The new budget is last_step + N, which can be smaller than the original run.steps for terminated runs (the confirmation prompt warns in this case). Pydantic enforces N >= 1 server-side.

This intentionally diverges from weco run and weco run derive, where --steps is the total budget for a fresh run. For resume, "more from here" matched user expectations better.