feat: 2D editing — floorplan panel, measurements, command palette (v0.3.0)

* sync: port 2D editing features from monorepo (v0.3.0)

## New Features

### Floorplan Panel (7.5K LOC)
- Full 2D editing interface with wall drawing, measurement, and unit display
- Interactive floorplan view with pan/zoom, grid snapping
- Wall thickness visualization, door/window placement
- Zone and slab polygon editing
- Guide image overlay support
- Metric/imperial unit toggle

### Command Palette Overhaul
- Complete rewrite with new command registry system
- Keyboard shortcuts UI with ShortcutToken component
- Editor-specific commands (floorplan, measurements, camera focus)
- Improved search and action organization

### Wall Measurements
- Real-time wall length labels in 3D view
- Metric/imperial conversion
- Wall measurement UI component

### Enhanced Tools
- Wall drafting utilities (grid snapping, validation)
- Node action menu for quick operations
- Improved polygon editing for zones/slabs/sites
- Roof segment panel for granular roof control

## Package Changes

### @pascal-app/core@0.3.0
- New wall-footprint.ts: 2D wall footprint calculation
- Wall mitering exports for floorplan view
- camera-controls:focus event
- Space detection undo pause/resume
- Mark sibling nodes dirty on deletion (miter recalc)

### @pascal-app/viewer@0.3.0
- ErrorBoundary component for robust item rendering
- Broken item fallback UI
- Wall renderer: mark dirty on mount
- Ground occluder: only lowest level punches through
- Unit state (metric/imperial) in viewer store

### @pascal-app/editor@0.1.0
- 48 file changes (16 new, 32 modified)
- New stores: useCommandRegistry, usePaletteViewRegistry
- Tree node drag-and-drop system
- Level selection utilities
- Enhanced scene graph operations

## Apps/Editor
- GeistPixelSquare font for pixel-perfect UI
- Blueprint icon asset
- Updated layout and globals for font support

## Security
- Zero AI imports or internal package refs
- All monorepo-specific code excluded
- Clean audit: no API keys or secrets

## Testing
- Security audit passed ✅
- All AI/internal code excluded ✅
- Version bumps applied ✅

79 files modified, 16 files added
~2600 insertions, ~1400 deletions

* fix: lint cleanup — suppress intentional dep warnings, fix missing dep, remove stale ignores

- Add biome-ignore for 3 intentional useEffect reset patterns (levelId, selectedGuide, selectedId)
- Fix actual missing dependency: currentBuildingId in handleSiteEditShortcutSelect callback
- Remove 3 stale biome-ignore comments in r3f.d.ts (rule not active)

Build and lint pass clean.

* fix: type errors — polygon area guards, selection cast, readonly keywords, door guard

- ceiling-panel, slab-panel, ceiling-tree-node, slab-tree-node, zone-tree-node:
  guard polygon[i]/polygon[j] array access before arithmetic (TS2532)
- scene.ts: introduce toViewerSelection() helper to cast persisted string IDs
  to branded template literal types expected by useViewer.setSelection (TS2345)
- door-panel: guard early return when node is undefined in setSegmentHeightRatio (TS18048)
- editor-commands: remove 'as const' from inline command object, keywords is mutable string[] (TS2322)

All type checks pass. Build and lint clean.

---------

Co-authored-by: Anton Pascal <anton-pascal@users.noreply.github.com>

packages/viewer/src/components/error-boundary.tsx

@@ -0,0 +1,16 @@
+import type { ErrorInfo, ReactNode } from 'react'
+import { Component } from 'react'
+
+export class ErrorBoundary extends Component<
+  { children: ReactNode; fallback: ReactNode },
+  { hasError: boolean }
+> {
+  state = { hasError: false }
+  static getDerivedStateFromError() {
+    return { hasError: true }
+  }
+  componentDidCatch(_e: Error, _i: ErrorInfo) {}
+  render() {
+    return this.state.hasError ? this.props.fallback : this.props.children
+  }
+}

packages/viewer/src/components/renderers/item/item-renderer.tsx

@@ -20,6 +20,7 @@ import { DoubleSide, MeshStandardNodeMaterial } from 'three/webgpu'
 import { useNodeEvents } from '../../../hooks/use-node-events'
 import { resolveCdnUrl } from '../../../lib/asset-url'
 import { useItemLightPool } from '../../../store/use-item-light-pool'
+import { ErrorBoundary } from '../../error-boundary'
 import { NodeRenderer } from '../node-renderer'
 
 // Shared materials to avoid creating new instances for every mesh
@@ -47,6 +48,17 @@ const getMaterialForOriginal = (original: Material): MeshStandardNodeMaterial =>
   return defaultMaterial
 }
 
+const BrokenItemFallback = ({ node }: { node: ItemNode }) => {
+  const handlers = useNodeEvents(node, 'item')
+  const [w, h, d] = node.asset.dimensions
+  return (
+    <mesh position-y={h / 2} {...handlers}>
+      <boxGeometry args={[w, h, d]} />
+      <meshStandardMaterial color="#ef4444" opacity={0.6} transparent wireframe />
+    </mesh>
+  )
+}
+
 export const ItemRenderer = ({ node }: { node: ItemNode }) => {
   const ref = useRef<Group>(null!)
 
@@ -54,9 +66,11 @@ export const ItemRenderer = ({ node }: { node: ItemNode }) => {
 
   return (
     <group position={node.position} ref={ref} rotation={node.rotation} visible={node.visible}>
-      <Suspense fallback={<PreviewModel node={node} />}>
-        <ModelRenderer node={node} />
-      </Suspense>
+      <ErrorBoundary fallback={<BrokenItemFallback node={node} />}>
+        <Suspense fallback={<PreviewModel node={node} />}>
+          <ModelRenderer node={node} />
+        </Suspense>
+      </ErrorBoundary>
       {node.children?.map((childId) => (
         <NodeRenderer key={childId} nodeId={childId} />
       ))}

packages/viewer/src/components/renderers/wall/wall-renderer.tsx

@@ -1,5 +1,5 @@
-import { useRegistry, type WallNode } from '@pascal-app/core'
-import { useRef } from 'react'
+import { useRegistry, useScene, type WallNode } from '@pascal-app/core'
+import { useLayoutEffect, useRef } from 'react'
 import type { Mesh } from 'three'
 import { useNodeEvents } from '../../../hooks/use-node-events'
 import { NodeRenderer } from '../node-renderer'
@@ -9,6 +9,11 @@ export const WallRenderer = ({ node }: { node: WallNode }) => {
 
   useRegistry(node.id, 'wall', ref)
 
+  // Mark dirty on mount so WallSystem rebuilds geometry when wall (re)appears
+  useLayoutEffect(() => {
+    useScene.getState().markDirty(node.id)
+  }, [node.id])
+
   const handlers = useNodeEvents(node, 'wall')
 
   return (

packages/viewer/src/components/viewer/ground-occluder.tsx

@@ -1,4 +1,4 @@
-import { useScene } from '@pascal-app/core'
+import { type LevelNode, useScene } from '@pascal-app/core'
 import polygonClipping from 'polygon-clipping'
 import { useMemo } from 'react'
 import * as THREE from 'three'
@@ -20,13 +20,39 @@ export const GroundOccluder = () => {
     s.lineTo(-size, size)
     s.closePath()
 
-    // Collect all polygons for slabs and zones
+    const levelIndexById = new Map<LevelNode['id'], number>()
+    let lowestLevelIndex = Number.POSITIVE_INFINITY
+
+    Object.values(nodes).forEach((node) => {
+      if (node.type !== 'level') {
+        return
+      }
+
+      levelIndexById.set(node.id, node.level)
+      lowestLevelIndex = Math.min(lowestLevelIndex, node.level)
+    })
+
+    // Only the lowest level should punch through the ground plane.
+    // Upper-level slabs should still cast shadows, but they should not
+    // reveal their footprint on the level-zero ground material.
     const polygons: [number, number][][] = []
 
     Object.values(nodes).forEach((node) => {
-      if (node.type === 'slab' && node.polygon && node.polygon.length >= 3) {
-        polygons.push(node.polygon as [number, number][])
+      if (!(node.type === 'slab' && node.visible && node.polygon.length >= 3)) {
+        return
       }
+
+      if (Number.isFinite(lowestLevelIndex)) {
+        const parentLevelIndex = node.parentId
+          ? levelIndexById.get(node.parentId as LevelNode['id'])
+          : undefined
+
+        if (parentLevelIndex !== lowestLevelIndex) {
+          return
+        }
+      }
+
+      polygons.push(node.polygon as [number, number][])
     })
 
     if (polygons.length > 0) {