IconRef: add url kind, point registered kinds at palette assets

User pointed at the palette's PNG icons in the bottom toolbar — they
expected the inspector title to use the same artwork, not the iconify
lucide glyphs. Different visual style.

- IconRef gains `{ kind: 'url'; src: string }`. Plain `<img>` render
  in ParametricInspector (no next/image — the inspector is
  `'use client'`).
- All currently-registered kinds switched to URL refs matching their
  palette `iconSrc`:
    fence    → /icons/fence.png
    slab     → /icons/floor.png
    ceiling  → /icons/ceiling.png
    wall     → /icons/wall.png
    spawn    → /icons/site.png
    shelf    → /icons/column.png (placeholder, same as palette)
- Kind-owned panels (slab/ceiling) already pass URL strings to their
  own PanelWrapper; unchanged.

Door/window/item will get URL refs when they register at Stage A.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

packages/core/src/registry/types.ts

@@ -230,6 +230,10 @@ export type IconRef =
   /** Iconify identifier, e.g. `lucide:square`. Matches the @iconify-react
    * setup the editor app already uses for tool icons. */
   | { kind: 'iconify'; name: string }
+  /** URL path to a raster or vector asset (PNG/SVG/...). Matches the
+   * palette's PNG/SVG assets — use this to share the same artwork
+   * between the bottom toolbar and the inspector title. */
+  | { kind: 'url'; src: string }
   /** Inline SVG path data. Use for asset packs or plugins that want a custom
    * mark without contributing a React component. */
   | { kind: 'svg'; viewBox: string; path: string }

packages/editor/src/components/ui/panels/parametric-inspector.tsx

@@ -137,6 +137,12 @@ export function ParametricInspector() {
 
 function renderIcon(ref: IconRef | undefined): React.ReactNode | undefined {
   if (!ref) return undefined
+  if (ref.kind === 'url') {
+    // Plain <img> here so the inspector doesn't pull in next/image's
+    // server-only requirements (the file is `'use client'`). Same
+    // 16x16 box the legacy panels use.
+    return <img alt="" className="h-4 w-4 shrink-0 object-contain" src={ref.src} />
+  }
   if (ref.kind === 'iconify') {
     return <Icon height={16} icon={ref.name} width={16} />
   }

packages/nodes/src/ceiling/definition.ts

@@ -86,7 +86,7 @@ export const ceilingDefinition: NodeDefinition<typeof CeilingNode> = {
   presentation: {
     label: 'Ceiling',
     description: 'A polygon-bounded ceiling surface that hosts ceiling-mounted items.',
-    icon: { kind: 'iconify', name: 'lucide:square-dashed' },
+    icon: { kind: 'url', src: '/icons/ceiling.png' },
     paletteSection: 'structure',
     paletteOrder: 40,
   },

packages/nodes/src/fence/definition.ts

@@ -94,7 +94,7 @@ export const fenceDefinition: NodeDefinition<typeof FenceNode> = {
   presentation: {
     label: 'Fence',
     description: 'A straight or curved fence segment with configurable posts and infill.',
-    icon: { kind: 'iconify', name: 'lucide:fence' },
+    icon: { kind: 'url', src: '/icons/fence.png' },
     paletteSection: 'structure',
     paletteOrder: 20,
   },

packages/nodes/src/shelf/definition.ts

@@ -64,7 +64,7 @@ export const shelfDefinition: NodeDefinition<typeof ShelfNode> = {
   presentation: {
     label: 'Shelf',
     description: 'A horizontal surface for stacking other items.',
-    icon: { kind: 'iconify', name: 'lucide:layers' },
+    icon: { kind: 'url', src: '/icons/column.png' },
     paletteSection: 'structure',
     paletteOrder: 50,
   },

packages/nodes/src/slab/definition.ts

@@ -83,7 +83,7 @@ export const slabDefinition: NodeDefinition<typeof SlabNode> = {
   presentation: {
     label: 'Slab',
     description: 'A polygon-bounded floor surface that hosts items on top.',
-    icon: { kind: 'iconify', name: 'lucide:square' },
+    icon: { kind: 'url', src: '/icons/floor.png' },
     paletteSection: 'structure',
     paletteOrder: 30,
   },

packages/nodes/src/spawn/definition.ts

@@ -52,7 +52,7 @@ export const spawnDefinition: NodeDefinition<typeof SpawnNode> = {
   presentation: {
     label: 'Spawn Point',
     description: 'Player or camera origin within a level. One per level.',
-    icon: { kind: 'iconify', name: 'lucide:flag' },
+    icon: { kind: 'url', src: '/icons/site.png' },
     paletteSection: 'structure',
     paletteOrder: 90, // bottom of structure list — matches legacy palette order
   },

packages/nodes/src/wall/definition.ts

@@ -82,7 +82,7 @@ export const wallDefinition: NodeDefinition<typeof WallNode> = {
   presentation: {
     label: 'Wall',
     description: 'A straight or curved wall segment. Hosts doors, windows, and wall-mounted items.',
-    icon: { kind: 'iconify', name: 'lucide:wall' },
+    icon: { kind: 'url', src: '/icons/wall.png' },
     paletteSection: 'structure',
     paletteOrder: 10,
   },