rendering: preserve material and lighting semantics in DrawList

[tritao]

Summary

This layer retains and executes the ordinary visual semantics that sit above the minimal DrawList executor:

• material fields: ambient, diffuse, specular, emissive, shininess, opacity, and shading model;
• directional, point, and spot lights, attenuation, two-sided lighting, and the explicit eight-light Visual-program cap;
• texture pixels, wrapping, effective filtering, mipmap policy, texture models, and blend color;
• depth, blend, alpha-test, transparency, and per-material primitive batching;
• composable GLSL material, texture, lighting, alpha-test, and shared surface-evaluation modules.

Traversal state remains semantic and renderer-neutral. The OpenGL executor owns backend fallbacks and diagnostics: missing lighting never synthesizes a headlight, dual-source blend factors are retained and warned/fallback only at execution, and retained lights beyond the Visual-program limit are reported rather than discarded from the IR.

This layer contains the private render-plan boundary and owns its opacity scheduling: opaque commands retain insertion order, while transparent commands use stable back-to-front ordering. Planner keys remain private and are never stored in semantic commands.

The shared VertexEvaluation.glsl and FragmentEvaluation.glsl modules are introduced here so ordinary visual roots and later raster consumers use one material/lighting evaluation contract.

Scope

This change does not add raster-width/point-size behavior, pixel image/text programs, picking, selection, manager orchestration, render stages, or context-loss lifecycle. Those remain in the layers above this one.

Validation

The retained semantic tests and shared GLFW/core pixel tests cover material, emissive, lighting, texture models, filtering, alpha, depth, blend, two-sided lighting, light-cap behavior, batching, and transparent depth-write behavior.

Stack

This layer owns the private planner boundary plus the frozen material, lighting, and opacity-scheduling contract consumed by the raster and manager layers above it.