Dragging a seam moved exactly the two tiles touching it, so a column edge
shared by several rows had to be dragged row by row and drifted out of line
in between.
A drag now moves that column boundary wherever it appears: every pair of
tiles meeting at the same x, in every row, travels with it. Each pair still
trades width within its own fixed span, so no row can push into another, and
the whole column stops at whichever row runs out of room first — one row's
minimum width holds the line for all of them. All rows move or none do; a
column edge that bends halfway is worse than one that won't budge.
Rows are only grouped by a shared seam. A row split somewhere else keeps its
own boundary, and a row where one tile simply spans across has no seam there
and stays put. Hovering a seam lights up the others that travel with it, so
what is about to move is visible before the drag starts.
Verified in the browser: two rows split at the same column move together from
one drag; rows split at different columns stay independent; a tall tile beside
two stacked ones resizes all three; and a 4-column drag stopped at 1 because
the lower tile's minimum width said so.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
