node:child_process — fork() + IPC (send/disconnect/'message'/channel) unimplemented #1933

Summary

child_process.fork(modulePath[, args][, options]) is not implemented. fork spawns a child running a Node module with an IPC channel wired up, exposing child.send(msg), child.on("message", …), child.disconnect(), and the connected/channel state.

This is the largest remaining piece of #1780. It depends on real async subprocess execution + an IPC channel (see the async-reactor issue), which Perry does not have today — every child currently runs synchronously to completion, so there is no live process to exchange messages with.

What to do

• Implement fork() returning a ChildProcess with a working IPC channel.
• child.send(message[, sendHandle][, options][, callback]) serializes message (JSON / advanced serialization) to the child.
• child.on("message", (msg) => …) fires when the child calls process.send(...).
• child.disconnect() closes the channel; connected flips to false, channel to null.
• The child side needs process.send / process.on("message") / process.connected / process.disconnect().

Note: in compiled-Perry there is no node to fork into — fork of a .ts/.js module path implies either re-spawning the compiled Perry binary with an entry selector, or compiling the forked module too. Scope the child-launch strategy as part of this ticket.

Parent: #1780. perry 0.5.1029.