feat(shader): Expand Gaussian blur to 13-tap wide distribution

- 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

tests/test_shader_manager.py

@@ -43,6 +43,23 @@ def test_blur_pipeline_compile_shaders():
   assert pipeline.h_blur_program is not None
   assert pipeline.v_blur_program is not None
 
+def test_blur_pipeline_wide_tap_distribution():
+ with patch("src.shader_manager.gl") as mock_gl:
+  mock_gl.glCreateProgram.return_value = 100
+  mock_gl.glCreateShader.return_value = 200
+  mock_gl.glGetShaderiv.return_value = mock_gl.GL_TRUE
+  mock_gl.glGetProgramiv.return_value = mock_gl.GL_TRUE
+  from src.shader_manager import BlurPipeline
+  pipeline = BlurPipeline()
+  pipeline.compile_blur_shaders()
+  assert mock_gl.glShaderSource.called
+  shader_sources = [call.args[1] for call in mock_gl.glShaderSource.call_args_list]
+  frag_sources = [s for s in shader_sources if 'texture(' in s and 'offset' in s]
+  assert len(frag_sources) >= 2
+  for src in frag_sources:
+   texture_calls = src.count('texture(u_texture')
+   assert texture_calls >= 11, f"Expected at least 11 texture samples for wide tap distribution, got {texture_calls}"
+
 def test_blur_pipeline_render_deepsea_to_fbo():
  with patch("src.shader_manager.gl") as mock_gl:
   tex_counter = iter([10, 20, 30])