Add a node that names the render layer of an object (#305)

The issue asked for Set render layer, Set sees and Render layer of. As
with #211, a probe showed that writing already works. A Properties
node of the object's type writes Render layer during a run, Inherit
included, and one of type Camera writes Sees. The next picture follows
both. As agreed, only Render layer of is built, and writing stays with
Properties.

- Render layer of is a data node with the input object and the outputs
  name and number. It answers the layer that holds, so an object
  without a choice of its own names its parent's.
- NodeContext.renderLayerOf answers the number with the same rule the
  drawing uses (renderLayerAlong). The new field renderLayers on
  GraphLookup brings the names to the node.
- hasRenderLayer in PropertySchema says which types are drawn.
- Decided here: for an object that is not drawn (a camera, a
  behavior, a collider) the name is empty and the number -1, as Layer
  of does without a collider.

Changing the render layer or Sees during a run had no test so far.
Three unit tests now hold the proof from the issue.

Tests:
- Gate: 231 files, 3534 tests (3526 + 8), exit 0
- e2e 6: 149 checks passed, e2e 63: 13 checks passed (+1)
- Unit: the coin moves into the overlay with Set and back with
  Inherit, a HUD container takes its sprite along, the main camera sees
  a second layer once its Sees is set, and Render layer of names the
  inherited layer, and none for a behavior
- Node catalog: four cases for Render layer of
- 63c3 moves a sprite onto UI in a Play run: the main camera no longer
  draws it, and the log reads "UI" and "1"
- Three counter-probes fail 1, 1 and 2 tests: without inheriting in
  the node, without the check for a drawn type, and without
  inheriting in the drawing
- "layer of" in the palette still finds Layer of first (6z-x)
- The e2e sum is 1731 (1730 plus 1)

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

src/core/graph/nodes/data/RenderLayerOf.ts

@@ -0,0 +1,22 @@
+import { layerName } from '../../../model/collisionLayers';
+import type { NodeDef } from '../../NodeRegistry';
+import { asEntity } from '../../values';
+import { num, obj, str } from '../shared';
+
+export const RenderLayerOf: NodeDef = {
+  type: 'RenderLayerOf',
+  label: 'Render layer of',
+  category: 'data',
+  description:
+    'The render layer an object is drawn on, by name and by number: its own, else the one it ' +
+    'inherits from its parent. For an object that is not drawn the name is empty and the number -1.',
+  inputs: [obj('object')],
+  outputs: [str('name'), num('number')],
+  params: [],
+  read: (ctx, _params, input, _def, lookup) => {
+    const target = asEntity(input('object'));
+    const layer = target ? ctx.renderLayerOf(target) : null;
+    if (layer === null) return { name: '', number: -1 };
+    return { name: layerName(lookup.renderLayers(), layer), number: layer };
+  },
+};