Perf: move the per-move wall/fence/roof draft END points into
useFloorplanDraftPreview; a new FloorplanLinearDraftLayer leaf owns the live
draft polygon + fence segment + wall measurement, subscribing to the store. The
shared FloorplanDraftLayer keeps only the per-click anchors. Wall/fence/roof
drafts now have zero per-move panel setState — buttery smooth like slab/zone.
Parity: migrate the remaining legacy Shift=bypass paths to the unified
mode-driven model. roof (move + click) honored only always-grid + bypassSnap —
now grid/lines/off (footprint → no angle). wall + fence click-commit still used
the legacy bypass while their move-preview didn't — now consistent. Wall Alt
stays 'commit single wall' (open product decision, untouched).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
