node:child_process — ChildProcess / Stream named exports unimplemented (#463 guard blocks gap-test compile) #1856

Summary

node:child_process now ships a real streaming spawn() ChildProcess plus execFile/execFileSync (#1780 / PR pending). The two remaining lines of the test_parity_child_process gap test are the named exports:

console.log("child_process.ChildProcess:", child_process.ChildProcess); // Node: [Function: ChildProcess]
console.log("child_process.Stream:", child_process.Stream);             // Node: undefined

Today a value-form reference to child_process.ChildProcess (i.e. read, not called) hits the #463 unimplemented-surface guard at compile time:

Error: `child_process.ChildProcess` is not implemented in Perry — see
`perry --print-api-manifest` ... (#463)

This blocks test_parity_child_process.ts from compiling at all, so the gap test can't be flipped even though the spawn/exec/execFile/sync surface it exercises now works.

What to do

• Expose child_process.ChildProcess as a callable/constructor value that prints [Function: ChildProcess] (a named function value is enough for the typeof/inspect probes; a working new ChildProcess() is a larger follow-up).
• child_process.Stream should resolve to undefined (Node does not export it).
• Together with # this is what's left to flip the test_parity_child_process gap test green.

Parent: #1780. perry 0.5.x.