refactor: Use lazy initialization for auxiliary textures

Prevents init/resize ordering bug and avoids unnecessary reallocation.

Changes:
- Auxiliary textures created on first use (compute/update_bind_group)
- Added ensure_texture() methods to defer registration until resize()
- Added early return in resize() if dimensions unchanged
- Removed texture registration from init() methods

Benefits:
- No reallocation on window resize if dimensions match
- Texture created with correct dimensions from start
- Memory saved if effect never renders

Tests: All 36 tests passing

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

4 files changed, 32 insertions, 12 deletions

diff --git a/src/gpu/effects/circle_mask_effect.cc b/src/gpu/effects/circle_mask_effect.cc
index aa9f324..08a9e33 100644
--- a/src/gpu/effects/circle_mask_effect.cc
+++ b/src/gpu/effects/circle_mask_effect.cc
@@ -26,11 +26,6 @@ CircleMaskEffect::~CircleMaskEffect() {
 void CircleMaskEffect::init(MainSequence* demo) {
   demo_ = demo;
 
-  const uint32_t width = width_;
-  const uint32_t height = height_;
-
-  demo_->register_auxiliary_texture("circle_mask", width, height);
-
   compute_params_.init(ctx_.device);
 
   // Initialize uniforms BEFORE bind group creation
@@ -157,10 +152,20 @@ void CircleMaskEffect::init(MainSequence* demo) {
   render_bind_group_ = wgpuDeviceCreateBindGroup(ctx_.device, &render_bg_desc);
 }
 
+void CircleMaskEffect::ensure_texture() {
+  if (!texture_initialized_ && demo_) {
+    demo_->register_auxiliary_texture("circle_mask", width_, height_);
+    texture_initialized_ = true;
+  }
+}
+
 void CircleMaskEffect::resize(int width, int height) {
+  if (width == width_ && height == height_)
+    return;
+
   Effect::resize(width, height);
 
-  if (!demo_)
+  if (!demo_ || !texture_initialized_)
     return;
 
   // Resize auxiliary texture
@@ -188,6 +193,8 @@ void CircleMaskEffect::resize(int width, int height) {
 
 void CircleMaskEffect::compute(WGPUCommandEncoder encoder,
                                const CommonPostProcessUniforms& uniforms) {
+  ensure_texture();
+
   uniforms_.update(ctx_.queue, uniforms);
 
   const CircleMaskParams params = {
diff --git a/src/gpu/effects/circle_mask_effect.h b/src/gpu/effects/circle_mask_effect.h
index 6ebaca1..91443d8 100644
--- a/src/gpu/effects/circle_mask_effect.h
+++ b/src/gpu/effects/circle_mask_effect.h
@@ -29,8 +29,11 @@ class CircleMaskEffect : public Effect {
   static_assert(sizeof(CircleMaskParams) == 16,
                 "CircleMaskParams must be 16 bytes for WGSL alignment");
 
+  void ensure_texture();
+
   MainSequence* demo_ = nullptr;
   float radius_;
+  bool texture_initialized_ = false;
 
   WGPURenderPipeline compute_pipeline_ = nullptr;
   WGPUBindGroup compute_bind_group_ = nullptr;
diff --git a/src/gpu/effects/cnn_effect.cc b/src/gpu/effects/cnn_effect.cc
index 84eb530..8673127 100644
--- a/src/gpu/effects/cnn_effect.cc
+++ b/src/gpu/effects/cnn_effect.cc
@@ -56,20 +56,25 @@ void CNNEffect::init(MainSequence* demo) {
   // Initialize uniforms BEFORE any bind group creation
   uniforms_.update(ctx_.queue, get_common_uniforms());
 
-  // Register captured_frame texture (used by all layers for original input)
-  if (layer_index_ == 0) {
-    demo_->register_auxiliary_texture("captured_frame", width_, height_);
-  }
-
   CNNLayerParams params = {layer_index_, blend_amount_, {0.0f, 0.0f}};
   params_buffer_.update(ctx_.queue, params);
 }
 
+void CNNEffect::ensure_texture() {
+  if (!texture_initialized_ && layer_index_ == 0 && demo_) {
+    demo_->register_auxiliary_texture("captured_frame", width_, height_);
+    texture_initialized_ = true;
+  }
+}
+
 void CNNEffect::resize(int width, int height) {
+  if (width == width_ && height == height_)
+    return;
+
   PostProcessEffect::resize(width, height);
 
   // Only layer 0 owns the captured_frame texture
-  if (layer_index_ == 0 && demo_) {
+  if (layer_index_ == 0 && demo_ && texture_initialized_) {
     demo_->resize_auxiliary_texture("captured_frame", width, height);
   }
 }
@@ -88,6 +93,8 @@ void CNNEffect::render(WGPURenderPassEncoder pass,
 }
 
 void CNNEffect::update_bind_group(WGPUTextureView input_view) {
+  ensure_texture();
+
   input_view_ = input_view;
 
   // Update common uniforms (CRITICAL for UV calculation!)
diff --git a/src/gpu/effects/cnn_effect.h b/src/gpu/effects/cnn_effect.h
index 1c9f0f3..f79fac7 100644
--- a/src/gpu/effects/cnn_effect.h
+++ b/src/gpu/effects/cnn_effect.h
@@ -35,9 +35,12 @@ class CNNEffect : public PostProcessEffect {
   }
 
  private:
+  void ensure_texture();
+
   int layer_index_;
   int total_layers_;
   float blend_amount_;
+  bool texture_initialized_ = false;
   WGPUTextureView input_view_;
   WGPUTextureView original_view_;
   UniformBuffer<CNNLayerParams> params_buffer_;