- Update horizontal and vertical blur shaders from 9-tap to 13-tap kernel - Use Gaussian weights with sigma=3.5 for creamier 'milky' blur effect - Add test_blur_pipeline_wide_tap_distribution to verify >= 11 texture samples - Weights: [0.0152, 0.0300, 0.0525, 0.0812, 0.1110, 0.1342, 0.1432] (symmetric) Task: Phase 1, Task 3 of frosted_glass_20260313 track