Fix docs callouts and logo theming

[thebuilder]

Summary

• replace the remaining guidance blockquotes with Blume note callouts
• restore a dark-mode fallback for the externally rendered README logo
• keep the inline docs header logo tied to the selected Blume theme

Why

GitHub renders the README logo as an external SVG, so it cannot inherit the page text color through currentColor. The logo became unreadable in GitHub dark mode after the responsive header work. The docs also had two guidance callouts rendered as plain blockquotes rather than native Blume callouts.

Impact

The README logo remains legible in both GitHub color schemes, the docs header continues to follow its active theme, and guidance content gets consistent callout styling.

Validation

• pnpm --filter docs exec blume check --isolated

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Project	Deployment	Actions	Updated (UTC)
react-intersection-observer	Ready	Preview	Jul 30, 2026 5:37pm

1 Skipped Deployment

Project	Deployment	Actions	Updated (UTC)
react-intersection-observer-storybook	Skipped		Jul 30, 2026 5:37pm

[pkg-pr-new]

npm i https://pkg.pr.new/react-intersection-observer@776

commit: 49e3fcc