ImageLightbox

A fullscreen image viewer rendered into document.body. It traps focus, locks page scroll and returns focus to the opener on close. Close with the X button, a click on the backdrop or Escape. With more than one image it shows previous and next buttons, dots and a counter, and ArrowLeft and ArrowRight navigate with wrap-around. UserMessage already opens it for attached images; use it directly for images elsewhere, such as tool output. It renders nothing when closed or when the active image has no url.