Add a reactive signal field

[ClaudiuSchuster]

Summary

• add a dependency-free Canvas signal field behind the existing Signal Observatory design
• respond to pointer movement with subtle parallax, lensing, and local signal connections
• preserve accessibility, privacy, static hosting, and deterministic build boundaries
• extend CSP, compression, immutable caching, and repository checks for the single local script

Validation

• ./scripts/check-repository.sh
• desktop visual and pointer-interaction review at 1280×720
• responsive review at 390×844 and 320×720
• no browser console warnings or errors
• no horizontal overflow at 320 CSS pixels
• prefers-reduced-motion hides the decorative Canvas layer

Performance and privacy

• 5,776 bytes of dependency-free JavaScript (8 KB budget)
• 114,429-byte initial transfer excluding the social preview (350 KB budget)
• no analytics, storage, cookies, third-party assets, or runtime network requests