perf: speed up uint8array scans with native Buffer indexOf
Context:
- Use Node native Buffer.indexOf in indexOfUint8Array when available.
- Use subarray instead of slice in removeFromUint8Array to reduce copies.
Benchmark (micro scenario, 300 iterations, 30 warmup, parent-file swap):
- Web continueStaticPrerender median: 4.873ms -> 0.658ms (+86.50% faster)
- Web continueDynamicHTMLResume median: 4.868ms -> 0.604ms (+87.59% faster)
