fix: use lazy loaders for stdio stream creation
Replace broken `globalThis.require` checks with `core.createLazyLoader()`
for node:net, node:fs, and node:tty. The previous code never worked in
Deno's polyfill context since `globalThis.require` is not set, causing
fallback paths that used non-imported ops to always run.
Also removes the setReadStream/setWriteStream injection pattern in favor
of lazy tty loading, and adds handle.unref() on stdio sockets to prevent
them from keeping the event loop alive.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
