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/runtime/systems/behaviorContext.ts

@@ -10,7 +10,9 @@ import type { Vec2 } from '../../core/model/Properties';
 import { JOINT_CONNECTED_KEY } from '../../core/model/joint';
 import { objectReference } from '../../core/model/objectRefs';
 import { findAsset, findAssetOf, findScene, type Project } from '../../core/model/Project';
+import { renderLayerAlong } from '../../core/model/renderLayers';
 import { soundFileOf } from '../../core/model/sound';
+import { hasRenderLayer } from '../../core/properties/PropertySchema';
 import { resolveAssetProps } from '../../core/properties/resolve';
 import { loopsOf, volumeOf } from '../../core/properties/sounds';
 import type { Entity } from '../Entity';
@@ -128,6 +130,15 @@ export function behaviorContext(
       const holder = found && layerHolderOf(world, found);
       return holder ? collisionFilterOf(holder.props).layer : null;
     },
+    renderLayerOf: (target) => {
+      const found = resolve(target);
+      if (!found || !hasRenderLayer(found.type)) return null;
+      return renderLayerAlong(
+        found,
+        (at) => at.props,
+        (at) => at.parent ?? null,
+      );
+    },
     ignoreOneWay: (target, seconds) => {
       const found = resolve(target);
       if (found) world.ignoreOneWay(found, seconds);