StructTypeNode: Fix inclusion when added to the layout.

[sunag]

Fixes: #30434

Description

Fix inclusion when added to the layout.

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	336.27 78.29	336.27 78.29	+0 B +0 B
WebGPU	517.08 143.61	517.16 143.63	+81 B +19 B
WebGPU Nodes	516.54 143.5	516.63 143.52	+81 B +20 B

🌳 Bundle size after tree-shaking

Minimal build including a renderer, camera, empty scene, and dependencies.

	Before	After	Diff
WebGL	465.25 112.13	465.25 112.13	+0 B +0 B
WebGPU	589.09 159.7	589.14 159.74	+53 B +43 B
WebGPU Nodes	544.45 149.25	544.5 149.3	+53 B +46 B