RHI: Add embedded shader source support via ShaderCompileDesc

- Add ShaderLanguage enum (HLSL, GLSL, SPIRV)
- Extend ShaderCompileDesc with source/sourceLanguage fields
- D3D12Device::CompileShader supports both file and embedded source
- OpenGLDevice::CompileShader supports embedded GLSL source
- Refactor test_shader.cpp to use embedded source for both backends

This enables consistent shader compilation across D3D12 and OpenGL
backends while maintaining backend-specific shader language support.

engine/src/RHI/OpenGL/OpenGLDevice.cpp

@@ -353,15 +353,40 @@ RHICommandQueue* OpenGLDevice::CreateCommandQueue(const CommandQueueDesc& desc)
 }
 
 RHIShader* OpenGLDevice::CompileShader(const ShaderCompileDesc& desc) {
-    std::wstring filePath = desc.fileName;
-    if (filePath.empty()) {
+    auto* shader = new OpenGLShader();
+    
+    if (desc.sourceLanguage == ShaderLanguage::GLSL && !desc.source.empty()) {
+        const char* sourceStr = reinterpret_cast<const char*>(desc.source.data());
+        ShaderType shaderType = ShaderType::Vertex;
+        
+        std::string profile(desc.profile.begin(), desc.profile.end());
+        if (profile.find("vs") != std::string::npos) {
+            shaderType = ShaderType::Vertex;
+        } else if (profile.find("ps") != std::string::npos || profile.find("fs") != std::string::npos) {
+            shaderType = ShaderType::Fragment;
+        } else if (profile.find("gs") != std::string::npos) {
+            shaderType = ShaderType::Geometry;
+        } else if (profile.find("cs") != std::string::npos) {
+            shaderType = ShaderType::Compute;
+        }
+        
+        if (shader->Compile(sourceStr, shaderType)) {
+            return shader;
+        }
+        delete shader;
         return nullptr;
     }
-    auto* shader = new OpenGLShader();
-    std::string entryPoint(desc.entryPoint.begin(), desc.entryPoint.end());
-    std::string profile(desc.profile.begin(), desc.profile.end());
-    shader->CompileFromFile(filePath.c_str(), entryPoint.c_str(), profile.c_str());
-    return shader;
+    
+    if (!desc.fileName.empty()) {
+        std::wstring filePath = desc.fileName;
+        std::string entryPoint(desc.entryPoint.begin(), desc.entryPoint.end());
+        std::string profile(desc.profile.begin(), desc.profile.end());
+        shader->CompileFromFile(filePath.c_str(), entryPoint.c_str(), profile.c_str());
+        return shader;
+    }
+    
+    delete shader;
+    return nullptr;
 }
 
 RHIPipelineState* OpenGLDevice::CreatePipelineState(const GraphicsPipelineDesc& desc) {