The agent settings UI unconditionally showed "You have access to Zed's
hosted models through your Organization" for all Business plan users,
even when the org admin had turned off the Zed AI model provider. Now
the copy reads "Zed's hosted models are disabled by your organization's
configuration" when is_zed_model_provider_enabled is false.

Also added component preview entries for both Business plan states.

Closes CLO-667

Release Notes:

- N/A

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Co-authored-by: Neel <neel@zed.dev>