[WeekendSuperhero]

Summary

• Replace live backdrop-filter with a pre-blurred background slice for multiple glass surfaces.
• Introduce useGlassBackdrop and usePublishAppBackground hooks to sync positions and publish background layers.
• Add GlassPrebakedDemo and update documentation for the new prebaked glass behavior.

Changes

• Styles: Add .glass-prebaked class avoiding layered rules and register non-inheriting --gx/--gy custom properties.
• Hooks: Create hooks for syncing viewport offsets and publishing app backgrounds.
• Components: Update GradientBackground and BackgroundProvider to publish background tokens. Add prebaked demo.
• Tests: Add unit tests for prebaked hooks and DOM syncing.

Test plan

• Verify GlassPrebakedDemo list scrolling keeps the frost background glued correctly.
• Ensure non-prebaked (live filter) fallback works on pattern or canvas backgrounds.
• Run test suite and confirm all glass-prebaked.test.tsx tests pass.

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PR description generated by Agent

[cloudflare-workers-and-pages]

Deploying sistine with    Cloudflare Pages

Latest commit:	107d767
Status:	✅  Deploy successful!
Preview URL:	https://9c2af8f1.sistine.pages.dev
Branch Preview URL:	https://weekendsuperhero-fake-glass.sistine.pages.dev

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