Tilemaps are a new placeable asset type that is painted with autotiles in the scene view, with layers, brush, eraser and rectangle, and is drawn at runtime and in the export (#128)

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/core/commands/require.ts

@@ -1,7 +1,16 @@
 /** Lookups that throw a `CommandError` when the target does not exist. */
 import { findNode, type Graph, type GraphEdge, type GraphNode } from '../graph/Graph';
 import { type NodeDef, nodeDef } from '../graph/NodeRegistry';
-import type { Asset, AutotileAsset, BehaviorAsset, StateMachineAsset, VariablesAsset } from '../model/Asset';
+import type {
+  Asset,
+  AutotileAsset,
+  BehaviorAsset,
+  StateMachineAsset,
+  TilemapAsset,
+  TilemapLayer,
+  VariablesAsset,
+} from '../model/Asset';
+import { findLayer } from '../model/tilemap';
 import { findObject, type ObjectTree } from '../model/hierarchy';
 import { isTemplateContent, objectRef, type ObjectRef } from '../model/instance';
 import {
@@ -85,6 +94,18 @@ export function requireAutotile(project: Project, assetId: string): AutotileAsse
   return asset;
 }
 
+export function requireTilemap(project: Project, assetId: string): TilemapAsset {
+  const asset = findAssetOf(project, assetId, 'tilemap');
+  if (!asset) throw new CommandError(`Tilemap ${assetId} not found`);
+  return asset;
+}
+
+export function requireTilemapLayer(project: Project, assetId: string, layerId: string): TilemapLayer {
+  const layer = findLayer(requireTilemap(project, assetId), layerId);
+  if (!layer) throw new CommandError(`Layer ${layerId} not found`);
+  return layer;
+}
+
 export function requireStateMachine(project: Project, assetId: string): StateMachineAsset {
   const asset = findAssetOf(project, assetId, 'statemachine');
   if (!asset) throw new CommandError(`State machine ${assetId} not found`);