Scaffold vpinball-wasm: Emscripten port of Visual Pinball

Build scripts, CMake/source patches, npm packaging, and a Gitea CI
workflow to compile the real Visual Pinball engine (SDL3 + WebGL2 +
libwinevbs for real VBScript) to WebAssembly.

The patches are validated end-to-end: the patched engine boots in a
real browser, loads a real .vpx table, compiles its real GLSL shaders,
computes environment map radiance, initializes physics, and starts the
VBScript engine, before hanging on the one deliberately-deferred piece
of work (game loop rewrite around emscripten_set_main_loop), documented
in the README's roadmap.

patches/libwinevbs/0001-winnt-wasm32-context-stub.patch

@@ -0,0 +1,34 @@
+diff --git a/wine/include/winnt.h b/wine/include/winnt.h
+index 477bd87..d9357fd 100644
+--- a/wine/include/winnt.h
++++ b/wine/include/winnt.h
+@@ -2043,6 +2043,29 @@ typedef ARM64_NT_CONTEXT CONTEXT, *PCONTEXT;
+ 
+ #endif /* __aarch64__ */
+ 
++#if defined(__LIBWINEVBS__) && defined(__EMSCRIPTEN__)
++/* libwinevbs-only: wasm32 has no real CPU context / SEH unwinding to describe.
++ * This library never performs structured exception handling or stack
++ * unwinding (no real threads, no SEH usage) - these types only need to exist
++ * so the unconditional NTSYSAPI declarations below type-check. */
++#define CONTEXT_FULL 0x1
++
++typedef struct _RUNTIME_FUNCTION
++{
++    DWORD dummy;
++} RUNTIME_FUNCTION, *PRUNTIME_FUNCTION;
++
++typedef struct _CONTEXT
++{
++    DWORD ContextFlags;
++} CONTEXT, *PCONTEXT;
++
++typedef struct _KNONVOLATILE_CONTEXT_POINTERS
++{
++    DWORD dummy;
++} KNONVOLATILE_CONTEXT_POINTERS, *PKNONVOLATILE_CONTEXT_POINTERS;
++#endif /* __LIBWINEVBS__ && __EMSCRIPTEN__ */
++
+ #if !defined(CONTEXT_FULL) && !defined(RC_INVOKED)
+ #error You need to define a CONTEXT for your CPU
+ #endif