Rework ReorderableColumn: the first cut measured each row, but grouped
cards have position-dependent padding, so slot heights varied and rows
snapped to the wrong places with no animation. Now rows are a fixed
uniform pitch, the target slot is the whole-pitches dragged, neighbours
slide aside with a spring, and the held row settles onto its slot before
the order commits. Add a lift (scale + shadow) on the held row and
cancel an in-flight settle if a new drag pre-empts it.
GroupedRow gains gapBelow so the reorderable list can own uniform
inter-row spacing.
On-device verified on Pixel 10.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Jean-Luc Makiola
37f0e22911