test(3d): screenshot-baseline TDD suite for the 3D viewer OpenGL->WebGL port — 47 native goldens + red-state WebGL harness

tests/3d-regression mirrors the gal-regression pattern at renderer scale:
shared C++ scenarios call real KiCad 3D-viewer code (opengl_utils, display
lists + DrawCulled stencil subtraction, MODEL_3D VBOs, private generators via
a rob-template accessor, and full reload()+Redraw() composites over a
synthetic BOARD_ADAPTER). A native macOS harness renders them on real OpenGL
into 47 committed goldens (bit-deterministic, FBO capture); the wasm harness
compiles the same TUs against wasm/stubs/gl_ffp_stub.c no-ops so every
scenario renders blank — the TDD red state (parity meter: 47/47 changed).
Comparisons use the CI pixelmatch engine via the new generic compare-dirs.ts
(floors.json levels; manifest.json cmp-guards registry drift).

Documents an upstream bug: appendPostMachiningGeometry's countersink path
adds middle quads without normals, silently erasing the walls of any
display list it is batched into (3d-post-machining.png keeps the lists
separate to record it).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

tests/3d-regression/native/config.h

@@ -0,0 +1,26 @@
+// Minimal config.h for native GAL test
+// Based on KiCad's generated config
+#ifndef KICAD_CONFIG_H
+#define KICAD_CONFIG_H
+
+// Version info
+#define KICAD_MAJOR_VERSION 8
+#define KICAD_MINOR_VERSION 0
+#define KICAD_PATCH_VERSION 0
+
+// Enable OpenGL
+#define KICAD_USE_OCC 0
+#define KICAD_USE_EGL 0
+
+// Platform detection
+#ifdef __APPLE__
+#define KICAD_MACOS 1
+#endif
+
+// Math
+#define KICAD_USE_STDROUND 1
+
+// Ensure types are properly sized
+#include <cstdint>
+
+#endif // KICAD_CONFIG_H