Read the pixel size of a texture in a graph (#262)

A graph had no way to know how big a picture is. An icon sprite with a
fixed size therefore stretched every icon of another size, an 8x8
pixel-art icon in a 16x16 slot was drawn twice as big.

- New data node Texture size. It takes a texture, a frame or a pixel
  art and hands out width and height in pixels, 0 x 0 for none.
  Wired into a sprite's width and height, the picture shows pixel for
  pixel.
- GraphLookup gets textureSize. The project answers it with the same
  pictureSize rule a sprite uses to size itself.

Tests:

- ./check.sh: 2749 tests, CHECK EXIT 0.
- 2 catalog cases (a picture, no picture) and one test against a real
  project: pixel-art sheet, single frame, missing texture.
- No e2e check and no counter-check for this node.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/core/model/graphLookup.ts

@@ -1,9 +1,11 @@
 import type { GraphLookup } from '../graph/lookup';
 import { startStateOf, statesOf, transitionsOf } from '../graph/stateMachine';
+import { pictureSize } from '../properties/aspect';
 import { resolveAssetProps } from '../properties/resolve';
 import { bagWithoutItemTypes } from './Properties';
 import { typeFields } from './structTypes';
 import { findAssetOf, type Project } from './Project';
+import { resolvePicture } from './texture';
 
 /**
  * What a graph may see of the project around it. A behavior's `defaults` are its variable values;
@@ -36,5 +38,9 @@ export function graphLookup(project: Project): GraphLookup {
       const asset = findAssetOf(project, assetId, 'struct');
       return asset ? { name: asset.name, fields: typeFields(asset).map((f) => f.key) } : null;
     },
+    textureSize: (pictureId) => {
+      const ref = resolvePicture(project, pictureId);
+      return ref ? pictureSize(ref) : null;
+    },
   };
 }