notion-react: add live coverage for upload-backed media and column width ratios once API support is proven

Context

• The public notion-react demo page now covers the current sync-safe surface end to end.
• Two Storybook surfaces remain intentionally excluded from live public syncs because the Notion API does not currently accept them reliably in our probes.

Gaps

• upload-backed media blocks (video, audio, file, pdf) reject external URLs on create and need the file_upload pipeline before they can be part of the rerunnable public demo
• column widthRatio / width_ratio is implemented in the local prop and host-projection surface, but live append probes against Notion still fail

Follow-up

• add an integration probe or e2e that proves the live API contract for each surface
• when a stable live path exists, replace the caveat entries on the public demo page with first-class synced examples
• decide whether width ratios should remain a local-only feature until live API support is available

Start with the notion-react public demo and the two excluded Storybook surfaces; review the current sync-safe examples and local widthRatio/width_ratio projection. Add integration probes or e2e coverage for video, audio, file, pdf, and column ratios, then replace demo caveats only after stable live API support is proven; record whether ratios remain local-only.