feat(paint-slots): add node.slots field to fence/stair/column/elevator schemas

Pre-adds the unified slot-ref field (Record<slotId, MaterialRef>) to the
four kinds being migrated onto the paint-slot model, so per-kind work can
proceed in parallel worktrees without cross-package core edits.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

packages/core/src/schema/nodes/column.ts

@@ -159,6 +159,9 @@ export const ColumnNode = BaseNode.extend({
   bracePlateEnabled: z.boolean().default(true),
   material: MaterialSchema.optional(),
   materialPreset: z.string().optional(),
+  // Unified paint-slot refs (`scene:`/`library:` MaterialRef per slot id),
+  // matching the slot model items/slab/shelf use. Absent = declared default.
+  slots: z.record(z.string(), z.string()).optional(),
 }).describe(dedent`
   Column node - used to represent structural or decorative pillars/columns.
   - style: visual approach such as plain, lathe-turned, carved, or cluster

packages/core/src/schema/nodes/elevator.ts

@@ -16,6 +16,9 @@ export const ElevatorNode = BaseNode.extend({
   type: nodeType('elevator'),
   material: MaterialSchema.optional(),
   materialPreset: z.string().optional(),
+  // Unified paint-slot refs (`scene:`/`library:` MaterialRef per slot id),
+  // matching the slot model items/slab/shelf use. Absent = declared default.
+  slots: z.record(z.string(), z.string()).optional(),
   position: z.tuple([z.number(), z.number(), z.number()]).default([0, 0, 0]),
   // Rotation around the Y axis in radians.
   rotation: z.number().default(0),

packages/core/src/schema/nodes/fence.ts

@@ -11,6 +11,9 @@ export const FenceNode = BaseNode.extend({
   type: nodeType('fence'),
   material: MaterialSchema.optional(),
   materialPreset: z.string().optional(),
+  // Unified paint-slot refs (`scene:`/`library:` MaterialRef per slot id),
+  // matching the slot model items/slab/shelf use. Absent = declared default.
+  slots: z.record(z.string(), z.string()).optional(),
   start: z.tuple([z.number(), z.number()]),
   end: z.tuple([z.number(), z.number()]),
   height: z.number().default(1.8),

packages/core/src/schema/nodes/stair.ts

@@ -31,6 +31,9 @@ export const StairNode = BaseNode.extend({
   treadMaterialPreset: z.string().optional(),
   sideMaterial: MaterialSchema.optional(),
   sideMaterialPreset: z.string().optional(),
+  // Unified paint-slot refs (`scene:`/`library:` MaterialRef per slot id),
+  // matching the slot model items/slab/shelf use. Absent = declared default.
+  slots: z.record(z.string(), z.string()).optional(),
   position: z.tuple([z.number(), z.number(), z.number()]).default([0, 0, 0]),
   // Rotation around Y axis in radians
   rotation: z.number().default(0),