Smooth-scroll POC

Compositor-driven infinite marquee (Web Animations API, iterations: Infinity, duplicated content, transform-only). Zero per-frame and per-wrap JavaScript — a busy main thread cannot stall the scroll.

• page-1 — bottom horizontal weather strip (production scrollingStrip look)
• page-2 — vertical scrolling news panel

Query params on both pages:

• ?speed=0.1..2.0 — portal slider range, px/sec = speed × 60 (default 1.0)
• ?jank=1 — block the main thread 600ms every 3s (simulates a heavy PBI zone); scroll must stay smooth
• ?hud=1 — main-thread FPS chip (dips during jank blocks while the scroll keeps moving)

Decisive on-device test: /page-1/?jank=1 in a split-screen next to a Power BI zone.