refactor(headless): convert nullptr checks to strippable macros

Added HEADLESS_RETURN_IF_NULL/HEADLESS_RETURN_VAL_IF_NULL macros
that compile to no-ops in STRIP_ALL/FINAL_STRIP modes.

Files updated:
- fatal_error.h: New headless check macros
- sequence.cc: NodeRegistry::create_texture
- post_process_helper.cc: Pipeline creation functions
- sampler_cache.h: SamplerCache::get_or_create
- bind_group_builder.h: Layout/group builders
- pipeline_builder.h: Shader and pipeline builders
- All effect constructors (7 files)

Headless tests passing. STRIP_ALL builds will have zero overhead.

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

1 files changed, 14 insertions, 13 deletions

diff --git a/src/effects/placeholder_effect.cc b/src/effects/placeholder_effect.cc
index a83d922..a014a71 100644
--- a/src/effects/placeholder_effect.cc
+++ b/src/effects/placeholder_effect.cc
@@ -1,6 +1,7 @@
 // Placeholder effect v2 implementation - logs TODO warning once
 
 #include "effects/placeholder_effect.h"
+#include "util/fatal_error.h"
 #include "gpu/post_process_helper.h"
 #include "gpu/shaders.h"
 #include <cstdio>
@@ -13,23 +14,23 @@ PlaceholderEffect::PlaceholderEffect(const GpuContext& ctx,
       sampler_(nullptr), name_(placeholder_name) {
   // Log once on construction
   fprintf(stderr, "TODO: %s not yet ported to v2, using passthrough\n", name_);
-  
+
+  // Headless mode: skip GPU resource creation (compiled out in STRIP_ALL)
+  HEADLESS_RETURN_IF_NULL(ctx_.device);
+
   uniforms_buffer_.init(ctx_.device);
   pipeline_ = create_post_process_pipeline(ctx_.device, WGPUTextureFormat_RGBA8Unorm,
                                            passthrough_v2_shader_wgsl);
 
-  // Headless mode: skip sampler creation
-  if (ctx_.device != nullptr) {
-    WGPUSamplerDescriptor sampler_desc = {};
-    sampler_desc.addressModeU = WGPUAddressMode_ClampToEdge;
-    sampler_desc.addressModeV = WGPUAddressMode_ClampToEdge;
-    sampler_desc.addressModeW = WGPUAddressMode_ClampToEdge;
-    sampler_desc.magFilter = WGPUFilterMode_Linear;
-    sampler_desc.minFilter = WGPUFilterMode_Linear;
-    sampler_desc.mipmapFilter = WGPUMipmapFilterMode_Nearest;
-    sampler_desc.maxAnisotropy = 1;
-    sampler_ = wgpuDeviceCreateSampler(ctx_.device, &sampler_desc);
-  }
+  WGPUSamplerDescriptor sampler_desc = {};
+  sampler_desc.addressModeU = WGPUAddressMode_ClampToEdge;
+  sampler_desc.addressModeV = WGPUAddressMode_ClampToEdge;
+  sampler_desc.addressModeW = WGPUAddressMode_ClampToEdge;
+  sampler_desc.magFilter = WGPUFilterMode_Linear;
+  sampler_desc.minFilter = WGPUFilterMode_Linear;
+  sampler_desc.mipmapFilter = WGPUMipmapFilterMode_Nearest;
+  sampler_desc.maxAnisotropy = 1;
+  sampler_ = wgpuDeviceCreateSampler(ctx_.device, &sampler_desc);
 }
 
 void PlaceholderEffect::render(WGPUCommandEncoder encoder,