ifcviewer-wgpu: wire Windows HWND surface creation

Without a Windows branch in `WgpuViewportWindow::createSurface()` we
were falling through to the `qWarning() << "wgpu surface creation not
yet wired for this platform"` else clause on Windows runs, causing
`init() -> createSurface()` to return false and the viewport to render
nothing (the user sees the Qt window's background fill — a white
viewport — and the log says "wgpu init failed; viewport will not
render in DebugView").

Add a `#elif defined(Q_OS_WIN)` branch that fills a
`WGPUSurfaceSourceWindowsHWND` chained-struct from
`GetModuleHandleW(nullptr)` (HINSTANCE) and `winId()` (HWND, as a Win32
window handle on the Qt Windows platform plugin), then passes it as
`surface_desc.nextInChain` to `wgpuInstanceCreateSurface`.

`<windows.h>` is pulled in inside the gated block with NOMINMAX and
WIN32_LEAN_AND_MEAN defined first so the preprocessor pollution
(`min`, `max`, etc.) doesn't leak into Eigen / `std::min`,`std::max`
elsewhere in the TU.

Note on the unrelated DXC log line the user also sees:

    [wgpu err] DxcCreateInstance failed:
    No such interface supported (0x80004002)

That is wgpu-native's DX12 backend probing for a modern
`dxcompiler.dll`. `E_NOINTERFACE` means a *too-old* dxcompiler.dll was
found on the system DLL search path (typical: a stale copy in
System32 / Visual Studio install). wgpu-native then falls back to its
Vulkan backend, so this log line is recoverable on its own — the
fatal failure was the missing surface branch above. If we hit shader
compilation issues after this lands, we can ship a known-good
dxcompiler.dll + dxil.dll alongside wgpu_native.dll separately.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/ifcviewer-wgpu/WgpuViewportWindow.cpp

@@ -1808,6 +1808,16 @@ bool WgpuViewportWindow::probeAndCreatePool() {
 #  if __has_include(<wayland-client-core.h>)
 #    include <wayland-client-core.h>
 #  endif
+#elif defined(Q_OS_WIN)
+// HINSTANCE for the surface descriptor. NOMINMAX + LEAN_AND_MEAN keep
+// <windows.h>'s preprocessor pollution out of Eigen / std::min,max.
+#  ifndef NOMINMAX
+#    define NOMINMAX
+#  endif
+#  ifndef WIN32_LEAN_AND_MEAN
+#    define WIN32_LEAN_AND_MEAN
+#  endif
+#  include <windows.h>
 #endif
 
 bool WgpuViewportWindow::createSurface() {
@@ -1852,9 +1862,19 @@ bool WgpuViewportWindow::createSurface() {
         qWarning().noquote() << "Unsupported Qt platform for wgpu surface:" << platform;
         return false;
     }
+#elif defined(Q_OS_WIN)
+    // wgpu-native maps WGPUSurfaceSourceWindowsHWND.hwnd to a Win32 HWND
+    // it never dereferences directly (it only hands the handle to D3D12 /
+    // Vulkan WSI). winId() is the HWND for top-level Qt windows on the
+    // Windows platform plugin, returned as WId (== quintptr).
+    WGPUSurfaceSourceWindowsHWND hwndsrc = {};
+    hwndsrc.chain.sType = WGPUSType_SurfaceSourceWindowsHWND;
+    hwndsrc.hinstance = ::GetModuleHandleW(nullptr);
+    hwndsrc.hwnd      = reinterpret_cast<void*>(static_cast<uintptr_t>(winId()));
+    surface_desc.nextInChain = &hwndsrc.chain;
+    surface_ = wgpuInstanceCreateSurface(instance_, &surface_desc);
 #else
-    // macOS / Windows native-handle wiring lands when those targets become
+    // macOS Metal surface wiring lands with task #32.
-    // active. Stage-1 development happens on Linux.
     qWarning() << "wgpu surface creation not yet wired for this platform";
     return false;
 #endif