Increase onboarding, profile, provider, and model UI coverage #2023

Summary

Add coverage for clean-runner onboarding and profile/provider/model UI flows.

Suggested coverage

• Welcome completed config skips onboarding.
• Clean config shows onboarding.
• Skip and save paths persist expected state.
• Profile create wizard validation.
• Provider/model loading errors and empty states.
• Provider/model switch cancellation and confirmation.

Test approach

Use unit and component tests for wizard steps and persistence. Add one tmux smoke for clean-runner onboarding behavior.