refactor(shaders): simplify comments in sdf_vector_simple_frag.glsl and update documentation

- Revised comments in `sdf_vector_simple_frag.glsl` to enhance clarity by removing references to the paper's HLSL code.
- Updated the description in `SDF_VECTOR_TEXTURES.md` to reflect a more accurate representation of the shader's features, emphasizing its simplified nature.

Author: timfox

src/shaders/SDF_VECTOR_TEXTURES.md

@@ -16,7 +16,7 @@ Full-featured implementation with:
 - Optional base color texture
 
 ### `sdf_vector_simple_frag.glsl`
-Simplified version closely matching the paper's HLSL code:
+Simplified version with minimal features:
 - Basic alpha testing
 - Soft edges
 - Outlining
@@ -135,8 +135,3 @@ fragColor = mix(shadow, main, step(0.5, dist));
 - **Memory**: A 64x64 SDF texture can represent vector art that would require 4096x4096 in traditional formats (64x memory savings)
 - **Performance**: Minimal overhead - typically 2-5 additional shader instructions
 - **Compatibility**: Works on all modern GPUs, including those without programmable shaders (using alpha testing)
-
-## References
-
-- Green, C. (2007). "Improved Alpha-Tested Magnification for Vector Textures and Special Effects". GPU Gems 3, Chapter 25.
-- Valve Corporation. Source Engine.

src/shaders/sdf_vector_simple_frag.glsl

@@ -12,7 +12,7 @@ layout(binding = 0) uniform sampler2D baseTextureSampler;
 // Optional base color texture
 layout(binding = 1) uniform sampler2D baseColorTexture;
 
-// Uniforms matching the paper's implementation
+// Uniforms
 layout(binding = 2) uniform SDFUniforms {
     // Soft edges
     bool SOFT_EDGES;
@@ -47,7 +47,7 @@ void main() {
 
     float distAlphaMask = texture(baseTextureSampler, v_texCoord).a;
 
-    // Apply outlining (matches paper's HLSL code)
+    // Apply outlining
     if (sdf.OUTLINE && 
         distAlphaMask >= sdf.OUTLINE_MIN_VALUE0 && 
         distAlphaMask <= sdf.OUTLINE_MAX_VALUE1) {
@@ -71,7 +71,7 @@ void main() {
         baseColor = mix(baseColor, sdf.OUTLINE_COLOR, oFactor);
     }
 
-    // Apply soft edges or alpha test (matches paper's HLSL code)
+    // Apply soft edges or alpha test
     if (sdf.SOFT_EDGES) {
         baseColor.a *= smoothstep(
             sdf.SOFT_EDGE_MIN,
@@ -83,7 +83,7 @@ void main() {
         baseColor.a = (distAlphaMask >= 0.5) ? 1.0 : 0.0;
     }
 
-    // Apply outer glow / drop shadow (matches paper's HLSL code)
+    // Apply outer glow / drop shadow
     if (sdf.OUTER_GLOW) {
         vec4 glowTexel = texture(
             baseTextureSampler,