Ensure all AI Experiments fail gracefully when no AI provider or credentials are configured. Users should receive clear, actionable guidance rather than errors, broken UI, or silent failures.

This applies to both editor-side interactions and admin settings.

Acceptance criteria:

• No experiment triggers fatal errors or broken UI without a provider
• Clear messaging explains why an action is unavailable
• Users are guided toward configuring a provider where appropriate
• Behavior is consistent across all experiments