fix: remove unnecessary @swc-node/register from webpack commands

[saschabuehrle]

Problem

The demo and build:react scripts were using node -r @swc-node/register to run webpack, which is unnecessary and causes issues:

1. Webpack is already JavaScript - The webpack executable at ./node_modules/.bin/webpack is a pre-built JavaScript file that doesn't need TypeScript compilation
2. Opens Node.js REPL - When node -r @swc-node/register runs without a filename, it opens the Node.js REPL instead of executing webpack
3. Unproductive workflow - Users have to Ctrl+C twice to exit the REPL before scripts can complete

Solution

Removed the unnecessary node -r @swc-node/register wrapper from both scripts:

• demo: Now uses webpack serve directly
• build:react: Now uses webpack directly

The @swc-node/register loader is only needed when running TypeScript files directly with Node.js, not when executing pre-built JavaScript binaries.

Testing

Both scripts should now:

• Execute webpack immediately without opening the Node.js REPL
• Complete faster without requiring manual intervention
• Maintain the same functionality (cross-env and webpack options preserved)

Fixes #299

Greetings, saschabuehrle