feat: make site motion perceptible

[Gnaroshi]

Summary

• strengthen Home hero entry with a 1s evidence-image settle and staggered copy movement
• draw page identity rails without moving heading geometry
• add scroll-linked section entry and a 4px two-color reading-progress indicator
• make buttons, cards, and approved evidence media respond visibly to hover and keyboard focus
• disable every new effect under prefers-reduced-motion and keep text at full contrast
• document and test normal-speed motion perceptibility

Motion evidence

• Home copy moves 28px into place while the hero image settles from 1.075 scale
• page rails animate from 0 to full height
• editorial sections rise 42px with CSS view timelines where supported
• evidence media reaches 1.055 scale with an inset teal/orange frame
• buttons and navigable surfaces lift 3px

Verification

• npm run check
• npm run build
• npm run check:i18n
• npm run check:public-tone
• npm run check:launch-content
• npm run check:links
• npm run test:e2e (178 passed, 5 fixture-dependent skipped)
• npm run test:a11y (55 passed)
• npm run test:performance (7 passed; Home JS 0KB, CLS 0.000)
• npm run test:visual (52 passed)
• npm run test:feed-contract (11 valid builds, 6 rejection fixtures)
• npm run check:interactive-controls (25 passed)
• npm run media:check
• npm run check:project-readiness

Review notes

The first implementation exposed two regressions during QA: a section scale affected card width measurement, and animated text opacity reduced contrast. Both were removed. The final implementation preserves layout geometry and full text contrast at every frame.