efactor(shader): migrate GLSL shaders to ShaderLab and clean up shader infrastructure

[zhuxudong]

Summary

• Migrate all built-in shaders from core/shaderlib (raw GLSL + rollup-plugin-glsl) to shader package as ShaderLab
  .shader files
• Reorganize shader package into Shaders/ (ShaderLab entry points) and ShaderLibrary/ (GLSL include fragments)
• Unify ShadowCaster/DepthOnly as shared Utility passes; PBR/BlinnPhong/Unlit/PBRSpecular use UsePass to reference them
• Remove ShaderChunkLoader and shader path/chunk loading infrastructure (_shaderRootPath, basePathForIncludeKey)
• Fix _resolveUsePass to support shader names containing "/" (e.g. Utility/ShadowMap)
• Restore original FXAA3_11.glsl without logic modifications

Motivation

Raw GLSL shaders scattered across core/shaderlib relied on rollup-plugin-glsl for bundling and lacked the render
state / pass structure that ShaderLab provides. This migration:

1. Consolidates all shader source into the shader package with a clear Shaders + ShaderLibrary layout
2. Enables ShaderLab features (render state declarations, UsePass, Editor properties) for built-in shaders
3. Removes the legacy shader chunk loading path — the engine now exclusively uses registerIncludes() for include
   registration and ShaderLab for shader creation

Key Changes

Shader Migration (packages/shader/)

• Shaders/: PBR, PBRSpecular, BlinnPhong, Unlit, Sprite, SpriteMask, Text, Trail, UIDefault, Skybox, SkyProcedural,
  BackgroundTexture, Particle, Blit, BlitScreen, ShadowMap, DepthOnly, PostProcess shaders (Bloom, SAO, FinalSRGB,
  FinalAntiAliasing, UberShader)
• ShaderLibrary/: All .glsl include fragments organized by category (Common, Lighting, PBR, Skin, Shadow, Fog,
  PostProcess, Particle)

UsePass Architecture

• Utility/ShadowMap and Utility/DepthOnly are canonical shared passes
• Material shaders reference them via UsePass "Utility/ShadowMap/Default/ShadowCaster"
• Registration order in registerShaders(): Utility first, then material shaders

Infrastructure Cleanup

• Delete ShaderChunkLoader, remove _shaderRootPath, basePathForIncludeKey from Preprocessor/ShaderLab/IShaderLab
• Shader.create() only accepts ShaderLab source (vertex/fragment string overload removed from implementation, kept as
  overload signature for now)
• _resolveUsePass parses from end to handle multi-segment shader names

Known Issue

• Precompile.test.ts suite fails at load time because FinalAntiAliasing.shader includes FXAA3_11.glsl which uses
  conditional #define type aliases (FxaaFloat, FxaaBool) — the Preprocessor collects these as macros causing parse
  failures. To be fixed on fix/shaderlab branch.

Test Plan

• npm run build passes
• npx vitest run tests/src/shader-lab/ — 62/62 tests pass
• ShaderLab parsing: PBR UsePass resolves correctly, render states preserved
• Precompile benchmark: _createFromPrecompiled round-trip works for PBR
• Verify no runtime regression with built-in materials (PBR, Unlit, BlinnPhong, etc.)

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