Phase A/B: fix the game loop and trim the asset payload

Phase A (the hard blocker): the engine now plays a real table live in
the browser via a real per-frame game loop, not just a static render.

Two real, previously-unknown upstream bugs found and fixed along the way:
- RenderDevice::WaitForVSync() unconditionally spawned a real std::thread
  every frame, even on __STANDALONE__ builds - a hard crash under
  Emscripten's single-threaded runtime (0003).
- The desktop game loop is a blocking native while loop with manual
  uSleep throttling, incompatible with a single-threaded WASM main
  thread. Adds Player::EmscriptenStepFrame() (one frame, no internal
  loop) driven by emscripten_set_main_loop, plus new JS-callable
  lifecycle entry points (vpinball_wasm_start/stop/dispose in the new
  src/core/EmscriptenBridge.cpp) that bypass the desktop main()/WinMain()
  chain entirely, since that chain assumes the process runs exactly one
  table to completion then exits (0004).

Verified end-to-end in Chrome: real .vpx load, real shader compilation,
real physics/script engine init, a real running frame loop (observed
advancing), and a clean stop() -> ~Player() teardown mid-session with
no crash or hang.

Phase B: trims the preloaded asset payload from ~51MB to ~11MB by
excluding editor-only bundled example tables and a Monaco code editor
never used by the player runtime, and adds real link-time optimization
(-O2 --closure 1) and --use-preload-cache for repeat visits.

scripts/build.sh

@@ -44,9 +44,17 @@ EMSCRIPTEN_LINK_FLAGS=(
    -sENVIRONMENT=web
    -sEXPORTED_RUNTIME_METHODS=FS,ccall,cwrap
    -sFORCE_FILESYSTEM=1
+   -sEXPORTED_FUNCTIONS=_main,_vpinball_wasm_start,_vpinball_wasm_stop,_vpinball_wasm_dispose
+   -sEXIT_RUNTIME=0
+   --use-preload-cache
 )
 if [ "$BUILD_TYPE" = "Debug" ]; then
-   EMSCRIPTEN_LINK_FLAGS+=(-sASSERTIONS=1 -sEXIT_RUNTIME=1)
+   EMSCRIPTEN_LINK_FLAGS+=(-sASSERTIONS=1 -O0)
+else
+   # CMAKE_BUILD_TYPE=Release only optimizes the compile step; emcc's link
+   # step needs its own -O level to actually run wasm-opt/dead-code
+   # elimination and (with --closure) minify the JS glue.
+   EMSCRIPTEN_LINK_FLAGS+=(-O2 --closure 1)
 fi
 
 emcmake cmake \