feat(immersive): increase source quality to 256x256

- Source canvas now 256x256 (was 64x64)
- Light pre-blur (8px), GPU shader does main blur
- Increased shader blur radius and samples (16 samples)
- Should produce much smoother results

src/lib/immersive/shaders/ambient.frag

@@ -31,8 +31,8 @@ const float BREATH_SPEED = 0.15;
 const float BREATH_AMOUNT = 0.08;
 
 // Blur simulation parameters
-const float BLUR_RADIUS = 0.015;  // UV space blur radius
-const int BLUR_SAMPLES = 12;      // Number of samples for blur
+const float BLUR_RADIUS = 0.025;  // UV space blur radius (increased for 256px source)
+const int BLUR_SAMPLES = 16;      // More samples for smoother blur
 
 // Simple pseudo-random function
 float random(vec2 st) {

src/lib/immersive/utils/texture-loader.ts

@@ -227,12 +227,12 @@ export async function loadBlurredTexture(
   activeLoads.set(requestId, controller);
 
   try {
-    // Generate blurred image
-    // Match original: 64x64 canvas with heavy blur (40px equivalent)
+    // Generate pre-processed image
+    // Use 256x256 for good quality - GPU shader will handle the blur
     const blurredDataUrl = await generateBlurredImage(
       artworkUrl,
-      64,   // Same as original CSS approach
-      20,   // Heavy blur - will be applied multiple times
+      256,  // Higher quality source for GPU blur
+      8,    // Light pre-blur, GPU shader does the heavy lifting
       controller.signal
     );