feat(procedural): add plasma, voronoi, normalmap generators

Add three new procedural texture generators:
- gen_plasma: classic sine-sum color texture (RGB output)
- gen_voronoi: Worley cellular noise (F1/F2/F2-F1 modes)
- gen_normalmap: post-process grayscale→RGB normal map

Remove gen_noise_256 (was an alias for gen_noise). Register new
generators in asset_manager and asset_packer. Add unit tests for
all three, and use them in test_3d_render (plasma sky, voronoi noise,
fBm normal map).

handoff(Gemini): plasma/voronoi/normalmap procedural generators added;
gen_noise_256 removed; tests + 3d_render usage wired up.

1 files changed, 37 insertions, 0 deletions

diff --git a/src/tests/3d/test_3d_render.cc b/src/tests/3d/test_3d_render.cc
index bd301bd..de9718e 100644
--- a/src/tests/3d/test_3d_render.cc
+++ b/src/tests/3d/test_3d_render.cc
@@ -102,6 +102,17 @@ bool gen_periodic_noise(uint8_t* buffer, int w, int h, const float* params,
   return procedural::make_periodic(buffer, w, h, p_params, 1);
 }
 
+// Wrapper: fBm noise → normal map
+bool gen_fbm_normalmap(uint8_t* buffer, int w, int h, const float* params,
+                       int num_params) {
+  (void)params; (void)num_params;
+  float fbm_params[] = {0.0f, 4.0f, 1.0f, 0.5f, 5.0f};
+  if (!procedural::gen_perlin(buffer, w, h, fbm_params, 5))
+    return false;
+  float nm_params[] = {8.0f};
+  return procedural::gen_normalmap(buffer, w, h, nm_params, 1);
+}
+
 int main(int argc, char** argv) {
   printf("Running 3D Renderer Test...\n");
 
@@ -134,6 +145,32 @@ int main(int argc, char** argv) {
 
   setup_standard_textures(g_renderer, g_textures, g_device, g_queue);
 
+  // Plasma → sky texture
+  ProceduralTextureDef plasma_def;
+  plasma_def.width = 256;
+  plasma_def.height = 256;
+  plasma_def.gen_func = procedural::gen_plasma;
+  plasma_def.params = {0.0f, 3.0f}; // time=0, freq=3
+  g_textures.create_procedural_texture("plasma", plasma_def);
+  g_renderer.set_sky_texture(g_textures.get_texture_view("plasma"));
+
+  // Voronoi (F2-F1 borders) → noise texture
+  ProceduralTextureDef voronoi_def;
+  voronoi_def.width = 256;
+  voronoi_def.height = 256;
+  voronoi_def.gen_func = procedural::gen_voronoi;
+  voronoi_def.params = {8.0f, 2.0f, 42.0f}; // scale=8, mode=F2-F1, seed=42
+  g_textures.create_procedural_texture("voronoi", voronoi_def);
+  g_renderer.set_noise_texture(g_textures.get_texture_view("voronoi"));
+
+  // fBm normal map (stored for material/debug use)
+  ProceduralTextureDef normalmap_def;
+  normalmap_def.width = 256;
+  normalmap_def.height = 256;
+  normalmap_def.gen_func = gen_fbm_normalmap;
+  normalmap_def.params = {};
+  g_textures.create_procedural_texture("normalmap", normalmap_def);
+
   // GPU Grid texture (additional texture for this test)
   GpuProceduralParams grid_params = {};
   grid_params.width = 256;