v0.7.0: SDL-free wasm worker backend (WebGPU + WebGL2) with on-demand assets

The engine now runs on a plain Web Worker (no SDL, no PROXY_TO_PTHREAD: in a pthread Emscripten proxies every filesystem syscall to the main browser thread, where synchronous XHR - and thus FS.createLazyFile - is forbidden). A page/worker pair transfers an OffscreenCanvas and forwards DOM input; assets load lazily from an embedded manifest, so entering a map fetches only that map and its tiles.

Presentation: ra3.webgpu (WebGPU via Emscripten's emdawnwebgpu port, WGSL shaders, the default on wasm) and ra3.wasmgl (WebGL2, GLSL ES). The legacy SDL ra3.webgl backend is removed.

scripts/make_web_manifest.py

@@ -0,0 +1,46 @@
+#!/usr/bin/env python3
+"""Generate the wasm lazy-asset manifest.
+
+The wasm build runs the engine on a worker, where synchronous XHR is legal, so
+assets are registered with ``FS.createLazyFile`` instead of being preloaded: the
+browser fetches each file only when the engine first opens it. This script lists
+every file under the assets root (as POSIX-relative paths) as
+``{"files": [...]}``; CMake preloads the manifest to ``/assets.manifest.json``.
+
+    scripts/make_web_manifest.py --root /path/to/assets --out assets.manifest.json
+
+Serve the tree at ``<wasm-root>/assets`` (or use ``serve.py --assets``).
+"""
+
+import argparse
+import json
+import os
+import sys
+
+
+def main() -> int:
+    parser = argparse.ArgumentParser(description="Generate the OpenRA3 wasm asset manifest")
+    parser.add_argument("--root", required=True, help="assets root to enumerate")
+    parser.add_argument("--out", required=True, help="manifest JSON to write")
+    args = parser.parse_args()
+
+    if not os.path.isdir(args.root):
+        print(f"root not found: {args.root}", file=sys.stderr)
+        return 1
+
+    files = []
+    for dirpath, dirnames, filenames in os.walk(args.root):
+        dirnames.sort()
+        for name in sorted(filenames):
+            rel = os.path.relpath(os.path.join(dirpath, name), args.root).replace(os.sep, "/")
+            files.append(rel)
+
+    with open(args.out, "w", encoding="utf-8") as handle:
+        json.dump({"files": files}, handle, separators=(",", ":"))
+        handle.write("\n")
+    print(f"wrote {args.out} ({len(files)} files)")
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())