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.

LICENSE

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+vpinball-wasm - WebAssembly port of Visual Pinball
+====================================================
+
+This repository's own original content (build scripts, CMake integration
+patches, the npm wrapper under package/, CI configuration, and documentation)
+is provided as-is with no additional restrictions beyond those imposed by the
+upstream projects it builds against.
+
+This project compiles and redistributes source from two upstream projects,
+each under their own license:
+
+1. Visual Pinball (https://github.com/vpinball/vpinball), fetched by
+   scripts/setup.sh into vendor/vpinball/. Visual Pinball is under a MIXED
+   license: it has been migrating file-by-file from a legacy "old MAME"-like
+   license to GPLv3+ since October 2020. Each file under GPLv3+ is marked
+   "// license:GPLv3+" at its top; any file without that marking remains
+   under the legacy license. See vendor/vpinball/LICENSE (present after
+   running setup.sh) for the full, authoritative text. Do not redistribute
+   built artifacts derived from this project without reading that file.
+
+2. libwinevbs (https://github.com/vpinball/libwinevbs), fetched by
+   scripts/setup.sh into vendor/libwinevbs/. Predominantly LGPL-2.1
+   (Wine-derived), with a small number of ATL header stubs of less certain
+   provenance - see vendor/libwinevbs/README.md's own License section.
+
+The small source patches this project applies to both projects (see
+patches/) are released under the same license as the file they modify.
+
+Because the final built .wasm/.js artifact statically links code from both
+upstream projects, its distribution terms are governed by their licenses,
+not solely by this repository's own (comparatively permissive) original
+content. If you are unsure what this means for your use case, consult the
+upstream LICENSE files directly rather than relying on this summary.