fix(onnxruntime): enable WASM threading to fix MLFloat16 build errors

- Add --enable_wasm_threads to ONNX Runtime build flags
- Fixes MLFloat16 missing methods (Negate, IsNegative, FromBits)
- Threading is safe for Node.js-only usage (no browser CORS concerns)
- Aligns with ONNX Runtime's recommended build path
- Resolves issue microsoft/onnxruntime#23769

Author: jdalton

packages/onnxruntime/scripts/build.mjs

@@ -145,6 +145,7 @@ async function build() {
     '--build_wasm',
     '--skip_tests',
     '--parallel',
+    '--enable_wasm_threads',
     '--cmake_extra_defines', 'onnxruntime_EMSCRIPTEN_SETTINGS=WASM_ASYNC_COMPILATION=0',
   ], {
     cwd: ONNX_SOURCE_DIR,