We Ralph Wiggumed WebStreams to make them 10x faster

Vercel profiled Next.js server rendering and found that WHATWG WebStreams (ReadableStream, WritableStream, TransformStream) were a major bottleneck due to per-chunk Promise allocations, microtask queue hops, and object overhead. They built `fast-webstreams`, a drop-in replacement that routes operations through Node.js's optimized `pipeline()` internally. Key optimizations include: zero-Promise piping by deferring pipeline construction until the full chain is known, synchronous resolution when data is already buffered, and a minimal `LiteReadable` for byte streams. Benchmarks show 10-14x throughput gains for common patterns—630 MB/s native vs ~6,200 MB/s for pipeThrough chains, and 110 MB/s vs 1,600 MB/s for the React Flight byte stream pattern. The library passes 1,100 of 1,116 Web Platform Tests. The work is also being contributed upstream to Node.js via a PR from Matteo Collina that adds fast paths directly to Node's native WebStreams implementation.