Merge Dev - Add --steps to weco resume

[aliroberts]

Add --steps to weco resume

Lets users extend a finished run with more evaluations instead of starting a fresh one.

Usage

weco resume --steps N # or -n N
Runs N more evaluations from the last node. The resume API resets run.steps to last_step + N.

Behaviour

• Completed runs: --steps is now required to resume (without it, the API returns 409 and the CLI
  prints a hint). Previously completed runs couldn't be resumed at all.
• Error / terminated runs: --steps is optional. Omit to keep the original budget; provide to
  extend (or shrink) it.
• Pre-run summary shows Total Steps: old → new and the count of additional evaluations. A yellow
  note is printed if the new total is less than the original budget.

Plumbing

• resume_optimization() gains additional_steps: Optional[int], forwarded to
  resume_optimization_run(..., steps=...).
• total_steps is refreshed from the resume response so the UI reflects the extended budget.

Version

0.3.35.