Add FPS counter, VSync toggle, shader metadata system, and multi-pass infrastructure

- FPS counter in window title (updates every 500ms)
- F4 key toggles VSync on/off
- Shader metadata: Name and Author from comments
- iChannel metadata parsing for multi-pass support
- Base structures: ShaderBuffer, ShaderPass
- FBO/texture management functions
- Updated all 11 shaders with Name/Author metadata

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

shaders/test.frag.glsl

@@ -1,3 +1,5 @@
+// Name: Test
+// Author: [TO_BE_COMPLETED]
 #version 330 core
 out vec4 FragColor;
 in vec2 vUV;