Smooth look on WebGPU: WGSL port fed by GPU inputs and CPU overrides (t88 phase 2c)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/manifest.json

@@ -53,6 +53,9 @@
     "render/gpu/colour.js",
     "render/gpu/shaders.js",
     "render/gpu/light.js",
+    "render/gpu/smooth-slope.js",
+    "render/gpu/smooth-shader.js",
+    "render/gpu/smooth.js",
     "render/gpu/device.js",
     "render/gpu/textures.js",
     "render/gpu/draw.js",