Run-control screen: select project/wave(s)/provider, start/stop/pause/resume

[Ryan-Atkinson87]

The run-control screen: select project, wave(s), and provider/plan, and start/stop and pause/resume the run.

Spec: §12 Run control, §4 run model.

Acceptance criteria

• Select project, wave(s), and provider/plan; start/stop and pause/resume controls, all driving the run-control API (Run-control API: project/wave/provider selection + start/stop/pause/resume #51) (§12).
• Available waves are loaded from the API (GitHub milestone state), not hardcoded.
• start/stop and pause are destructive/consequential actions — confirm before firing (frontend bar).
• Loading, empty, error, and populated states all handled (frontend bar).
• No hardcoded API URLs; WCAG 2.1 AA on the new screen.
• Tests: control actions call the right API endpoints (API mocked); confirm-before-fire on stop/pause; error state renders on API failure.

Depends on: #60, #51