The floating scroll-to-top button sat on the footer's “Support” link at the end of every page from 768 to ~1600 px

at the page's end: no footer link under the button at 1440/1024/768 in Compact and Full and at the XL scale; "Support" → button 31 px; at 1920 Compact and on phones the crops are byte-identical to the old build. shell.spec "at a page's end scroll-to-top sits clear" fails on the old build.

tailwindcss@4, other: CSS container query units (cqw) with percentage margins

the button, 20 px above the panel's bottom and 32 px in from its edge, cleared the one-line footer.

at a page's end it covered "Support" (37 px into the footer band) at 768, 1024, 1280 and 1440 px in the Compact layout and at every width in Full; at 1920 Compact the centred 1440 px row ended 80 px from the edge, so nothing touched.

the footer row is max-w-content mx-auto; it reaches the edge whenever the panel is narrower than 1440 px plus its padding, or the layout is Full.

before/after crops at 1440 @2× light and dark; a Full-layout probe (old: −29 px, new: +31 px).