Fizlet 0.1.0

E1, the kernel:

• createEngine: one shared requestAnimationFrame for every engine, fixed 60 Hz step with a catch-up cap, read → step → render phases, render alpha, advance() for headless runs.
• Auto-pause: hidden tab, page leaving, root off screen, typing in the host's fields; reduced motion opt-in. One AbortSignal tears everything down.
• Pool (bounded, prefilled, never grows), EventRing (fixed capacity, cleared each frame), seeded random (the DOM VIRUS core sequence, allocation-free, restorable state).
• Ledger: text, styles, attributes, classes and added nodes; change-only writes; restore() gives the page back exactly (style text byte for byte) and a newer host edit always wins.
• stats(): frames, steps, dropped time, frame ms, pools, events, ledger size, pause reasons.
• fizlet/debug: guardLayout(engine) counts layout reads during a step.
• fizlet/ui: the Board UI kit and spec, moved here from DOM Battlefield.
• Contract tests: one rAF for N engines, fixed step + cap, pause, bounded pools and events, seeded random, destroy, zero allocation over 1M steps, exact DOM restore, host edits win, auto-pause, layout guard. Size budgets in CI (kernel ~2.6 KB of 4 KB gzip).