WT.7 Wall + Grid: lock walls to grid lines so they move with the grid

Wall tool spec page 9, 'How other tools combine with the wall' (Duncan, 2026-11-05), tracked at /roadmap-internal 'BimCraft wall tool specification'. Code checked in the a Discord member source 2026-11-05. Spec: snap walls to grid lines and lock them; move a grid line and its walls move with it (Hold -> Place in space -> Join solver; today Partly). Today (model-grids.js): grids are drawn, IfcGrid lines from other programs are read for display and snapping only; walls snap to them while drawing but nothing remembers the link, so moving a grid line moves no wall. Wanted: a wall end or location line can be locked to a grid line (the Hold block, with WT.3 Lock), moving the grid runs the join solver. OTHER APPS: CadCraft has grids too; build the lock once. Not started.

walls-09 2026-11-06: Built in /lab: Properties › Lock to grid (a wall along a grid line, or an end on one), stored with the Hold block; Grid tool › pick a line › Move by (new: the UI could not move a grid line before) moves the line and the locked walls follow with their joined walls, one undo step; renaming keeps the lock, deleting the line drops it; moving a locked wall off its line is refused; a turned line that cannot keep the lock is refused. Recipes in lib/walls (host-free; copied to bimcraft/a Discord member/walls by tools/walls/sync.mjs), BimCraft adapter wall-tools.js + wall-tools-ui.js. Tests: node lib/walls/test/test.mjs (59/0, known answers worked out in the file), node bin/test-bimcraft.mjs --walltools (all ok, incl. the spec's nine tests: all Pass), real page tools/bimcraft-test/browser-walltools.mjs 33/0. Help: wall-tools (en). NOT done: CadCraft grids, SuperCad adapter, hand check (WT.7-HAND).

walls-plan-09 2026-11-06 (done): see docs/0.9-sessions/walls-plan-09.md.