perf: finish the mobile field and interaction budget

[parvbansal11]

Outcome

Finishes the post-deployment performance and accessibility pass without changing the field-versus-instrument design.

• Uses a cohesive touch-aware coarse-pointer simulation capped near 20 fps on mobile.
• Keeps the full slow-pointer constellation, fast-pointer split, obstacle routing, topology mutation, and depth treatment on fine-pointer desktops.
• Removes the reduced-motion delay that temporarily hid the playground break and downstream impact.
• Raises interactive controls in the hero, playground, and setup sheet to at least 44 CSS pixels.
• Keeps the static reduced-motion field on the correct light or dark rendering path.
• Synchronizes verified proof metrics and generated brand assets against the core repository in CI.
• Adds grouped weekly updates for pinned GitHub Actions.

Verification

• Mobile Lighthouse: 99 Performance, 100 Accessibility, 100 Best Practices, 100 SEO
• Desktop Lighthouse: 100 in all four categories
• FCP 1.2 s, LCP 1.8 s, CLS 0, TBT 0 ms on the mobile audit
• Zero interaction long tasks under 4x CPU throttling
• Pointer interaction frame time: p95 9.2 ms, p99 9.4 ms, maximum 10.3 ms
• No horizontal overflow at 320, 390, 768, or 1440 px
• Reduced-motion candidate state shows the stopped rail, break marker, impact, and witness immediately
• Setup sheet traps focus, closes with Escape, restores focus, locks background scrolling, and stays inside the mobile viewport
• No external runtime requests
• Static integrity, JavaScript syntax, no-em-dash, local-link, proof, and generated-asset checks pass

The public proof now reflects 115 passing tests and 93.08 percent coverage from the merged core source.