feat: leverage libp2p v3 features in remote communications

[sirtimid]

Context

With the libp2p v3 upgrade (#900) complete, several new features are now available but not yet used. These could improve error handling, observability, and composability of our remote communications layer.

Features to evaluate

• Stream middleware — node.use('/protocol', async (stream, connection, next) => { ... }) for Express-like composable protocol handling. Could add cross-cutting concerns (logging, metrics, auth) to the 'whatever' protocol handler without modifying the core handler logic.

• Async protocol handlers with auto-abort — In v3, handler rejections automatically abort the stream. Our handlers in connection-factory.ts are currently synchronous callbacks. Making them async would propagate errors properly instead of silently dropping them.

• Fine-grained stream close events — v3 streams emit close events with { error, local } properties, distinguishing "I closed it" vs "remote closed it" and "clean close" vs "error close". This could improve error handling in transport.ts and reconnection logic.

• Stream backpressure API — v3 streams have .pause()/.resume() and .send() returns false when buffered. We use byteStream() which abstracts this, but for high-throughput scenarios the lower-level API could be useful.

• @libp2p/utils stream utilities — Beyond byteStream(), there's lpStream (length-prefixed) and pbStream (protobuf). Could replace custom framing if we ever need structured messaging.

Priority

None of these are urgent — the upgrade gives us the foundation. Evaluate and adopt incrementally based on actual pain points.