Found in review (CodeRabbit): the last fix located a camera click by the pointer, which can have
moved on by the end of the release's frame. A click pressed on page 2 and released on page 1,
with the pointer back on page 2 by then, moved the quadrilateral to page 2. `PagePointer` keeps
each release's position, so `PagePointer::released` gives where the click came up, and the click
is located there.
Test: `a_camera_click_released_off_its_page_moves_nothing`, seen failing without the fix.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>