feat(LiveProvider): add opt-in server-rendered previews

[tujoworker]

Summary

LiveProvider previews are currently client-only. Rendering examples on the server by default would be unsafe because it could unexpectedly execute consumer code, browser-dependent code, or side effects during a server request.

This adds an explicit ssr prop for trusted, deterministic examples. Synchronous previews render in the initial server response without repeating the transform after hydration. Asynchronous transforms stay empty on the server, reuse the client hydration promise, and ignore stale results from older edits. Existing consumers remain client-only by default.

[vercel]

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[changeset-bot]

🦋 Changeset detected

Latest commit: 188edc8

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
react-live	Minor

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[tujoworker]

Hi @ryan-roemer. This is now rebased onto v5 and reworked as opt-in SSR through an ssr prop, disabled by default. It includes hydration, error, update, and async race coverage, plus a changeset. The full Node 24 build and test matrix passes locally.

GitHub Actions is waiting for maintainer approval because this is an external contribution, and Vercel also needs team authorization. Would you have time to approve CI and review the API direction? Feedback on whether this approach fits the project would also be very helpful.