feat(ugc): opt-in metal and glow shader groups in made models

Player models are multishader (RenderComponent shader 100): the client
wraps each NiLODNode and draws it with the mapShaders id in its name.
With shader_metal, shader_brushed or shader_glow set, the opaque bricks
are split by look into S<id>_Metal_Model, S<id>_Brushed_Model and
S<id>_Glow_Model beside S01_Opaque_Model and S01_Alpha_Model, each with
every LOD level. Metal is LU Toolbox's metallic colors plus Materials.xml
types (shinySteel; brushedSteel and matteSteel for brushed), glow its
glow colors. Glow shapes get an emissive material (glow_emissive) and
their plain color, not the baked one. Transparent glow stays in S01_Alpha.

All off by default, which writes the same bytes as before (tested). Not
how live looked; models already made change only when made again.

The icon renderer reads the groups back by tag and draws glow at its
plain color and metal with a tinted reflection and highlight.

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

dUgcServer/UgcRender.h

@@ -55,10 +55,15 @@ namespace UgcRender {
 		float contrast{ 1.0f };      // around the middle grey of the sRGB result
 		float shadows{ 1.0f };       // how much the sun's shadows darken, 0 to 1
 		AoOptions ao{ false, 5.0f, 32, 1.0f, 0.0f };
+		float glowEmissive{ 1.0f };  // how far glowing shapes go from lit to their plain color (the glow_emissive setting)
 	};
 
 	// The model drawn from the icon's camera, framed to fit, on a transparent background. `opaqueAo`: the opaque mesh's
 	// ambient occlusion (AmbientOcclusion) when it is known already, else it is worked out when options.ao wants it.
+	// Opaque vertices with a look (UgcModel::Mesh::looks) are drawn roughly as the game's shaders draw them: GLOW goes
+	// from lit to its plain color by glowEmissive (LEGO-Emissive), METAL and BRUSHED dim the diffuse light and add a
+	// sky-and-ground reflection tinted by the color and a highlight, sharp for polished metal and broad for brushed
+	// steel (Polished Metal, Brushed Steel: an environment map tinted by the vertex color).
 	Image RenderIcon(const UgcModel::Model& model, const IconOptions& options, const std::vector<float>* opaqueAo = nullptr);
 
 	struct OptimizeOptions {