refactor: create node-native debug channel instead of bridging web streams
When __NEXT_USE_NODE_STREAMS is enabled, createDebugChannel() now creates
a Node.js Writable directly as the server side instead of a web
WritableStream. This eliminates the web-to-node bridge that was needed
in renderToFlightPipeableStream.
React's renderToPipeableStream (Node API) expects debugChannel to be a
Node Writable (checks typeof .write === 'function'). Previously, passing
{ writable: WritableStream } caused React to enable debug info production
without a drain destination, hanging the flight stream.
Also updates vendored React types in $$compiled.internal.d.ts to add
the debugChannel option to renderToPipeableStream and widen the web
API types to accept the DebugChannelServer union.