Process.run ends the run on the Node host instead of running the program #1468

What you did

bend main.bend -o main.js, then node main.js, with main.bend the file below (a Process.run of /bin/echo). The standalone JS program is a verification lane recent fixes check on Node too (#1446, #1450), and AGENTS.md names the loader "for bun and node".

What happened

Under Bun the program prints the child's output and exits 0. Under Node the run ends before any answer:

$ bun main.js
Done 0 [hello
] []
end

$ node main.js
ReferenceError: Worker is not defined
        at process_run (...)
exit 1

A host without Bun has no global Worker and no Bun.spawn, so Process.run cannot run its worker and the ReferenceError ends the run through io_errs: the effect never answers, and every computation after it is lost. The same host abort hits the effects that bind libc through bun:ffi (File.read, File.read_bytes, File.read_at, TCP., UDP., Socket.close, Listener.close), which end with Error: Cannot find module 'bun:ffi'; those may be a design call (answer Fail on a host without FFI, or grow node paths), so I am keeping this issue on Process.run, which has a direct fix: node:child_process.spawnSync is the semantics the C lane models (#1392), and the fix PR runs on it.

Measured on current main (5e70819), Linux x86_64: the permanent tests/io/process_run.bend, emitted standalone and run under Node with the fix branch, answers all 19 rows True, including timeout (ETIMEDOUT), the combined output cap (EFBIG), a runaway descendant past the cap, exit and signal codes, and a missing executable (ENOENT).

The file

import Base

def show(r: Result<&1, &1, U32 & String, U32 & (String & String)>) -> String:
  match r:
    case Done{(code, (out, err))}:
      "Done " ++ U32.show(code) ++ " [" ++ out ++ "] [" ++ err ++ "]"
    case Fail{(c, m)}:
      "Fail " ++ U32.show(c) ++ " " ++ m

def main() -> IO(Unit):
  do IO<Unit>:
    a : Result<&1, &1, U32 & String, U32 & (String & String)> <-
      Process.run("/bin/echo", ["hello"], "", 4096, 3000)
    x : Unit <- IO.print(show(a))
    IO.print("end")

bend --version

main at 5e70819 (after 2.0.36), run through bun 1.4.2 and node v22.14.0

uname -sm

Linux x86_64

clang --version (the first line)

Debian clang version 14.0.6 (unrelated: the C lane was not part of this repro)