motion's function-form useTransform subscribes only to the values its first run reads: an early return froze the cards

each card's distance returned early while the stage was still unmeasured (if (!g.measured) return k0), before it read offset. Its first run never read offset, so it never subscribed to it. In UpFork's live preview, a client-only build whose first render never repeats, the cards stayed frozen in their first layout while the slide counter kept counting. In the Next.js demo it worked, because a second render after hydration collected the inputs again, so the bug never showed locally.

commit 98e4f3c; the test "moves the cards themselves, in a render that never repeats (a client-only app, UpFork's preview)".