chore(src/gpu): remove stale cnn_v1/v2 artifacts and dead comments

- demo_effects.h: drop commented-out cnn_v1/v2 includes (will be removed)
- gpu.cc: replace stale "V2:" migration comments with accurate descriptions
- effect.h, sequence.h: drop redundant #ifndef guards (kept #pragma once)

handoff(Gemini): stale comment cleanup in src/gpu/ — no logic changes

4 files changed, 4 insertions, 15 deletions

diff --git a/src/gpu/demo_effects.h b/src/gpu/demo_effects.h
index 77e5c76..1f859bc 100644
--- a/src/gpu/demo_effects.h
+++ b/src/gpu/demo_effects.h
@@ -38,8 +38,4 @@
 #include "../../cnn_v3/src/gbuf_view_effect.h"
 #include "../../cnn_v3/src/gbuf_deferred_effect.h"
 
-// TODO: Port CNN effects
-// #include "../../cnn_v1/src/cnn_v1_effect.h"
-// #include "../../cnn_v2/src/cnn_v2_effect.h"
-
 #include <memory>
diff --git a/src/gpu/effect.h b/src/gpu/effect.h
index 6c50d84..70ba9be 100644
--- a/src/gpu/effect.h
+++ b/src/gpu/effect.h
@@ -1,7 +1,5 @@
 // Effect: Base class for effects with multi-input/multi-output support
 
-#ifndef EFFECT_H
-#define EFFECT_H
 #pragma once
 
 #include "gpu/gpu.h"
@@ -98,4 +96,3 @@ class Effect {
   // Auto-passthrough helper for 1:1 input/output effects
   void blit_input_to_output(WGPUCommandEncoder encoder, NodeRegistry& nodes);
 };
-#endif // EFFECT_H
diff --git a/src/gpu/gpu.cc b/src/gpu/gpu.cc
index a463a10..0be5afe 100644
--- a/src/gpu/gpu.cc
+++ b/src/gpu/gpu.cc
@@ -252,7 +252,7 @@ RenderPass gpu_create_render_pass(WGPUDevice device, WGPUTextureFormat format,
   pipeline_desc.multisample.mask = 0xFFFFFFFF;
   pipeline_desc.fragment = &fragment_state;
 
-  // No depth stencil for v2 effects (v1 removed)
+  // No depth stencil for post-process effects
   pipeline_desc.depthStencil = nullptr;
 
   pass.pipeline = wgpuDeviceCreateRenderPipeline(device, &pipeline_desc);
@@ -437,12 +437,11 @@ void gpu_init(PlatformState* platform_state) {
 
   InitShaderComposer();
 
-  // V2: Sequences initialized by InitializeV2Sequences() called from main
 }
 
 void gpu_draw(float audio_peak, float aspect_ratio, float time, float beat_time,
               float beat_phase) {
-  // V2: Rendering handled by RenderV2Timeline() called from main
+  // Rendering is driven externally via the sequence pipeline
   (void)audio_peak;
   (void)aspect_ratio;
   (void)time;
@@ -456,7 +455,7 @@ void gpu_resize(int width, int height) {
   g_config.width = width;
   g_config.height = height;
   wgpuSurfaceConfigure(g_surface, &g_config);
-  // V2: Resize handled by RenderV2Timeline() framebuffer recreation
+  // Framebuffer recreation is handled externally by the sequence pipeline
 }
 
 const GpuContext* gpu_get_context() {
@@ -468,5 +467,5 @@ WGPUSurface gpu_get_surface() {
 }
 
 void gpu_shutdown() {
-  // V2: Shutdown handled by sequence cleanup
+  // Cleanup is handled by sequence and platform shutdown
 }
diff --git a/src/gpu/sequence.h b/src/gpu/sequence.h
index 04482fb..51c8af1 100644
--- a/src/gpu/sequence.h
+++ b/src/gpu/sequence.h
@@ -1,7 +1,5 @@
 // Sequence: DAG-based effect routing with ping-pong optimization
 
-#ifndef SEQUENCE_H
-#define SEQUENCE_H
 #pragma once
 
 #include "gpu/gpu.h"
@@ -126,4 +124,3 @@ class Sequence {
   UniformsSequenceParams params_;
   UniformBuffer<UniformsSequenceParams> uniforms_buffer_;
 };
-#endif // SEQUENCE_H