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, 5 insertions, 8 deletions

diff --git a/src/gpu/bind_group_builder.h b/src/gpu/bind_group_builder.h
index 3b25ba9..49b7ebe 100644
--- a/src/gpu/bind_group_builder.h
+++ b/src/gpu/bind_group_builder.h
@@ -20,6 +20,7 @@ typedef struct WGPUSamplerImpl* WGPUSampler;
 typedef uint32_t WGPUShaderStageFlags;
 
 #include "platform/platform.h"
+#include "util/fatal_error.h"
 
 class BindGroupLayoutBuilder {
   std::vector<WGPUBindGroupLayoutEntry> entries_;
@@ -93,10 +94,8 @@ class BindGroupLayoutBuilder {
   }
 
   WGPUBindGroupLayout build(WGPUDevice device) {
-    // Headless mode: skip bind group layout creation
-    if (device == nullptr) {
-      return nullptr;
-    }
+    // Headless mode: skip bind group layout creation (compiled out in STRIP_ALL)
+    HEADLESS_RETURN_VAL_IF_NULL(device, nullptr);
     WGPUBindGroupLayoutDescriptor desc{};
     desc.entryCount = entries_.size();
     desc.entries = entries_.data();
@@ -134,10 +133,8 @@ class BindGroupBuilder {
   }
 
   WGPUBindGroup build(WGPUDevice device, WGPUBindGroupLayout layout) {
-    // Headless mode: skip bind group creation
-    if (device == nullptr) {
-      return nullptr;
-    }
+    // Headless mode: skip bind group creation (compiled out in STRIP_ALL)
+    HEADLESS_RETURN_VAL_IF_NULL(device, nullptr);
     WGPUBindGroupDescriptor desc{};
     desc.layout = layout;
     desc.entryCount = entries_.size();