ProtocolTransportPaths

Live byte stream.

Lazy: not materialised unless accessed. On first access the stream is seeded with every byte already accumulated (partialBytes) and then wired to future chunks. For URL-sourced blocks, first access triggers fetch() and pipes the response body through.

Repeated access returns the same ReadableStream reference — you can safely read it once, release the lock, and re-acquire a reader later (e.g. React StrictMode effect re-invokes). The standard ReadableStream.locked semantics prevent concurrent readers; use stream.tee() when you truly need multiple live consumers.