Ceiling and slab tools: switch cursor tracking to per-frame raycasting onto a level plane (useFrame) instead of relying on grid:move events, and memoize Raycaster/Plane to reduce allocations. Update line geometry updates to be performed imperatively from the frame loop, ensure previews only trigger React updates when the snapped display position changes, and keep cursor/preview snapping consistent with user-visible pointer. Add sceneRegistry-based fallback to resolve a level's Y position (used by Grid, CeilingTool and SlabTool) when the level mesh isn't registered yet, computing Y from level node data and viewer levelMode. Misc: import/add necessary three.js types and small refactors to visibility/reset logic.
