A quick one-finger flick toward a free side of the active page, once
that edge is on screen, highlights and pulses the plus button on that
side for three seconds. It never adds a page by itself, so ordinary
panning can't create pages; a tap on the highlighted plus does.
Fling detection lives in ink/fling.ts with tests.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01GaoZtJQZwLXkEgWs8twCia
