fix: preserve vinext RSC compatibility on GitHub Pages

[owjs3901]

Summary

• port the proven devup-ui.com static-export RSC transport to the Pages demo
• install the transport inline before hydration and preserve automatic prefetch
• pin the vinext deployment ID and restore required response metadata
• rewrite clean RSC requests to exported .rsc artifacts while preserving the visible URL
• apply the /yeollin-cms asset prefix inside RSC payloads

Why devup-ui.com worked

devup-ui.com already ships this dedicated transport and is hosted at the domain root. Yeollin CMS previously installed a partial adapter later from a client Provider and did not prefix RSC asset references for a project Pages subpath.

Verification

• TypeScript check passed
• oxlint passed with one pre-existing auth warning
• production demo build prerendered 22 routes with 0 skipped
• content, media, and redirects RSC payloads contain only /yeollin-cms/_next asset URLs
• generated HTML contains the early transport, fixed deployment ID, static artifact rewrite, and visible URL restoration