Loads pos-app.js in a sandbox iframe, pre-populates a cart, and runs the long-press flow. The status box below reports each step.
The iframe loads pos-config.js, theme.js, letterhead-config.js, and pos-app.js from this server. Before loading, we set localStorage['pos.cart'] to a fake cart entry so the boot picks it up. The same-origin iframe can read the cart state via window.__pos.openEditLine(id), which is what the long-press timer calls internally.
Step 3 dispatches a synthetic pointerdown on the cart line, waits 700ms (timer is 600ms), then checks if the modal opened.
This is a temporary test page. Delete it after the bug fix is verified.