FX.96 CadCraft GRIDMOVE carried a whole plan wall that only starts on the grid line

Found by walls-plan-09 while locking walls to grid lines (WT.7): GRIDMOVE treats a block reference whose insert point lies on the line as a column and moves it whole, and a plan wall is a block reference, so a wall that merely STARTS on the grid line (the room's north wall at its east end) travelled away whole instead of being stretched. Fixed in gridmove.js: a plan wall is judged by its ends: an end on the line goes with it, both ends on the line move the wall whole, otherwise the wall stays. Test: node tools/cadcraft-test/walls-plan.mjs (WALLGRID then GRIDMOVE: east wall follows, south and north walls shorten, west wall stays). In /lab, not hand-tried: part of WTPLAN-HAND.