[proggeramlug]

Summary

Closes the two follow-ups left from the streaming-spawn work (#1780 / #1858), which together make the test_parity_child_process gap test byte-identical to node --experimental-strip-types.

#1856 — child_process.ChildProcess / Stream named exports

A value-form read of child_process.ChildProcess (e.g. console.log(child_process.ChildProcess)) tripped the #463 unimplemented-surface gate at compile time, which blocked the whole gap test from compiling. Now:

• ChildProcess is registered in the API manifest (as a class) and added to the runtime callable-export list, so it reads as [Function: ChildProcess].
• Stream is registered as a manifest property and resolves to undefined (Node does not export it).
• The console function formatter now falls back to the closure's own name property when no name is registered for the (shared bound-method) function pointer — so bound native exports print their real name. This also nudges events.EventEmitter / tty.ReadStream toward Node's output; no parity fixture asserted the old [Function (anonymous)].

#1857 — util.promisify(exec) / promisify(execFile)

main's general util.promisify (shipped separately) resolves to the single first-result value — but Node attaches a custom promisify hook to exec/execFile that resolves to { stdout, stderr }. Added a detection at the top of util_promisify::js_util_promisify: when the argument is the bound child_process.exec/execFile export, it returns a child_process-specific wrapper that runs the command (Perry's synchronous model) and yields an already-resolved Promise of { stdout, stderr }. exec/execFile also join the callable-export list so child_process.exec reads as a function (typeof === "function").

Test

• test_parity_child_process (the canonical gap test) is now byte-identical to Node — removed from test-parity/known_failures.json.
• New focused regression test test-files/test_issue_1856_1857_exports_promisify.ts (exports + promisify(exec/execFile)) is byte-identical.
• Existing spawn-stream test still passes; cargo fmt --all --check clean; API docs regenerated.

Built on top of the merged #1858; integrates with main's general util.promisify rather than duplicating it.