Mobile: desks and help tips fall off phone screens

Operator report 2026-09-14: things falling off the display on the phone. At 360 px the scrolling shell (.dsc-root-body) scrolled sideways: Overview 385 px (bare 1fr / implicit grid tracks cannot shrink below nowrap label min-content: triad 305 → zone card 339 → page 373), Plants › Roster 513 px (plants table not in .dsc-table-scroll), and ? help popovers opened off the right edge (601 px on phone, 1253 px on a 1024 desktop) and were painted over by the next animated page section. Fixed in ecc3128 (fix/mobile-overflow): minmax(0,1fr) tracks, table scroll wrappers, HelpTip viewport clamp + open-section lift. Verified in the preview at 360 px and desktop against the sim brain; not yet on the Pi or a real phone browser.