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, 23 insertions, 0 deletions

diff --git a/src/gpu/effects/shader_composer.h b/src/gpu/effects/shader_composer.h
new file mode 100644
index 0000000..7d918a9
--- /dev/null
+++ b/src/gpu/effects/shader_composer.h
@@ -0,0 +1,23 @@
+// This file is part of the 64k demo project.
+// It defines the ShaderComposer class for managing WGSL snippets.
+
+#pragma once
+
+#include <string>
+#include <map>
+#include <vector>
+
+class ShaderComposer {
+public:
+    static ShaderComposer& Get();
+
+    // Register a snippet (e.g. "common_math", "sdf_primitives")
+    void RegisterSnippet(const std::string& name, const std::string& code);
+
+    // Assemble a final shader string by prepending required snippets
+    std::string Compose(const std::vector<std::string>& dependencies, const std::string& main_code);
+
+private:
+    ShaderComposer() = default;
+    std::map<std::string, std::string> snippets_;
+};