Enable preview URLs for docs Worker versions

[Kludex]

Summary

The Docs preview: sticky comment on PRs has been empty (e.g. #1077, #1078): the workflow interpolates steps.deploy.outputs.deployment-url, but wrangler versions upload only prints the Version Preview URL line that populates the output when preview URLs are enabled for the Worker. This adds preview_urls = true to wrangler.toml.

Note: preview URLs are served on workers.dev, so the account's workers.dev subdomain must be registered (one-time dashboard setting) for wrangler to print the URL.

AI Disclaimer

This PR was developed with the assistance of either Claude or Codex. I've reviewed and verified the changes.

[github-actions]

Docs preview:

[codspeed-hq]

Merging this PR will not alter performance

✅ 15 untouched benchmarks
⏩ 7 skipped benchmarks¹

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_{Comparing enable-docs-preview-urls (363ed97) with main (e111465)}

Footnotes

1. 7 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩