Summary

This PR addresses a resource management issue where HTTP response bodies were not being properly released if the stream was cancelled by the consumer. By implementing the cancel hook in the ReadableStream constructor, we ensure that the internal dropBody() logic is triggered, preventing memory leaks and hanging connections.

Problem

Previously, the implementation only handled AbortSignal events. However, if a user:

1. Manually called reader.cancel(), or
2. Exited a for await...of loop early via break or return,
   The ReadableStream would stop, but the underlying resources managed by dropBody() remained active.

Solution

Added the cancel property to the ReadableStream source object to bridge the gap between the Web Stream lifecycle and our internal resource management.

// Ensure cleanup if the consumer cancels the stream
cancel: () => dropBody()

Fixes #3227