Clarify OpenUI Cloud benefits in CLI setup

[zahlekhan]

Summary

• make OpenUI Cloud the recommended starting point in openui create help and the interactive backend picker
• surface its hosted models, managed conversation history, built-in tools, and ready-to-use report and presentation artifacts
• clarify that self-hosting is the option for teams that specifically need to own the provider, AI route, and persistence
• align the CLI package README, quickstart, and CLI reference with the new guidance

Why

The previous copy named the two templates but did not clearly explain how much backend infrastructure OpenUI Cloud manages. This update presents the concrete, currently supported benefits so developers can make a better-informed choice without overstating either option.

User impact

New projects receive a clearer default recommendation and a more useful comparison at the point where developers choose their backend.

Validation

• pnpm --filter @openuidev/cli run ci
• pnpm --filter @openuidev/cli run build
• manually verified openui create --help
• manually verified the interactive backend picker