feat(3d): Implement Task 21.1 WGSL Library & Composer

- Implemented ShaderComposer for modular WGSL snippet management.
- Factored out common math, primitives, lighting, and ray-box helpers.
- Refactored Renderer3D to use dynamic shader composition.
- Consolidated high-DPI and shadow robustness fixes into final shader structure.

1 files changed, 33 insertions, 0 deletions

diff --git a/src/gpu/effects/shader_composer.cc b/src/gpu/effects/shader_composer.cc
new file mode 100644
index 0000000..61da6e6
--- /dev/null
+++ b/src/gpu/effects/shader_composer.cc
@@ -0,0 +1,33 @@
+// This file is part of the 64k demo project.
+// It implements the ShaderComposer class.
+
+#include "gpu/effects/shader_composer.h"
+#include <sstream>
+
+ShaderComposer& ShaderComposer::Get() {
+    static ShaderComposer instance;
+    return instance;
+}
+
+void ShaderComposer::RegisterSnippet(const std::string& name, const std::string& code) {
+    snippets_[name] = code;
+}
+
+std::string ShaderComposer::Compose(const std::vector<std::string>& dependencies, const std::string& main_code) {
+    std::stringstream ss;
+    ss << "// Generated by ShaderComposer\n\n";
+    
+    for (const auto& dep : dependencies) {
+        auto it = snippets_.find(dep);
+        if (it != snippets_.end()) {
+            ss << "// --- Snippet: " << dep << " ---\n";
+            ss << it->second << "\n";
+        }
+    }
+    
+    ss << "// --- Main Code ---\n";
+    ss << main_code;
+    
+    return ss.str();
+}
+