[Test] (WGL): add manual Windows smoke tests - hand-rolled WGL bootstrap and GLFW-driven variant covering the zero-area helper-window path

tools/wgl-smoke/README.md

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+# WGL smoke tests
+
+Manual bring-up tests for the Windows host layer (drop-in `opengl32.dll`).
+Both replicate the GLFW/LWJGL bootstrap Minecraft uses and verify a rendered
+triangle via `glReadPixels`; exit code 0 means pass.
+
+- `wgl_smoke.cpp` - hand-rolled Win32/WGL sequence (dummy context on a hidden
+  helper window, ARB pixel format + 3.2 core forward-compatible context,
+  gdi32 pixel-format forwarding, swap loop, readback).
+- `glfw_smoke.cpp` - the same flow driven by a real GLFW binary, which also
+  exercises GLFW's zero-area helper window (the case that needs the
+  DirectVulkan no-swapchain-at-init path).
+
+Build (x64 Native Tools prompt), with GLFW binaries for the second test:
+
+    cl /nologo /EHsc /W3 wgl_smoke.cpp user32.lib gdi32.lib
+    cl /nologo /EHsc /W3 glfw_smoke.cpp /I%GLFW%\include %GLFW%\lib-vc2022\glfw3dll.lib user32.lib gdi32.lib
+
+Run with the MobileGL `opengl32.dll` copy (and `glfw3.dll`, plus ANGLE's
+`libEGL.dll`/`libGLESv2.dll`/`d3dcompiler_47.dll` for DirectGLES) in the exe
+directory:
+
+    set MOBILEGL_BACKEND_TYPE=DirectVulkan   (or DirectGLES)
+    set MOBILEGL_LOG_FILE_PATH=smoke.log
+    wgl_smoke.exe && glfw_smoke.exe