docs(registry): clarify catalog preview staging and published URLs

[jrusso1020]

The registry contribution guide presents the local snapshot path as the published catalog image. Explain local PNG staging, the uploaded CDN URL, and the existing manifest poster override, including previews without a poster. Clarify that the upload script runs from the repository checkout.

Successor to #1949 by @tianma-if; original authorship preserved. Regenerated the official skill manifest because this guide is installed skill content.

Validation: traced preview generation, catalog-index generation and upload script; checked 171 explicit poster URLs and the poster-less preview against the current index; local links also resolve in a copied skill. Only the registry skill hash changes. Formatting, manifest check and applicable commit hooks pass.

[miguel-heygen]

Reviewed ae3730489173a5c10e9a2f756b2c1e55d30c798e.

skills/hyperframes-registry/references/contributing.md:121 correctly separates local snapshot staging from published CDN URLs and preserves the existing explicit-poster/no-poster behavior. Traced thumbnail generation, upload destination and catalog-index generation; all 171 explicit posters and the one posterless preview agree with the current index. Original @tianma-if authorship is preserved, and the manifest diff changes only this skill hash.

No findings. Verified source and index data; no CDN upload or render was performed. The skill-manifest and skill checks pass in CI.

No prior reviews or comments were present at precheck. CI has no failed checks at this check, but pending checks remain; this approval is on code/documentation merits and is not a CI-complete or merge-ready claim.

— Magi

Verdict: APPROVE
Reasoning: The change matches the current implementation and no blocking regression was found within the stated verification scope. Required CI must still finish successfully.