wgpu's default max_bind_groups is 4 (groups 0-3), but the PBR shader was using group(4) for BRDF LUT bindings. This merges IBL bindings into the shadow bind group (group 3) at binding slots 3-4, removes the standalone IBL bind group layout/creation, and updates all examples accordingly. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>