fix(3d): restore correct orientation in test_3d_render (direct-to-surface)

Add Renderer3D::set_direct_render(bool) flag (must be set before init()).
When true, uses standard CCW winding and un-negates perspective Y, restoring
the pre-ba7ea27 orientation for direct-to-surface rendering where the
post-process Y-flip is absent.

handoff(Gemini): set_direct_render() is the escape hatch for any future
renderer usage that bypasses the post-process chain.

1 files changed, 5 insertions, 0 deletions

diff --git a/src/3d/renderer.h b/src/3d/renderer.h
index 11a7931..8f933b5 100644
--- a/src/3d/renderer.h
+++ b/src/3d/renderer.h
@@ -78,6 +78,10 @@ class Renderer3D {
     bvh_enabled_ = enabled;
   }
 
+  // Call before init(). When true, renders directly to surface (no post-process
+  // Y-flip): uses standard perspective (Y not negated) and CCW winding.
+  void set_direct_render(bool v) { direct_render_ = v; }
+
   struct MeshGpuData {
     WGPUBuffer vertex_buffer;
     WGPUBuffer index_buffer;
@@ -120,6 +124,7 @@ class Renderer3D {
 
   BVH cpu_bvh_; // Keep a CPU-side copy for building/uploading
   bool bvh_enabled_ = true;
+  bool direct_render_ = false; // true = render to surface (no post-process flip)
 
   std::map<AssetId, MeshGpuData> mesh_cache_;
   const MeshGpuData* temp_mesh_override_ = nullptr; // HACK for test_mesh tool