NXS browser demos

Served with COOP/COEP so SharedArrayBuffer and worker scenarios work.

• Benchmark (NXS vs JSON vs CSV)Parse, random access, and reducer scenarios — up to large fixture sizes.
• Ticker60 FPS in-place byte patch vs full JSON re-parse.
• WorkersFour workers, shared buffer, zero bytes copied between threads.
• Log explorerVirtual scroll over a large line-oriented view.