node:child_process — execSync/execFileSync do not throw on non-zero exit

[proggeramlug]

Summary

execSync / execFileSync do not throw on a non-zero exit. Node throws an Error (with the command output attached) when the child exits non-zero:

try { cp.execSync("exit 4"); } catch (e) {
  // Object.keys(e) → status, signal, output, pid, stdout, stderr
  // e.status === 4
}

Today (perry 0.5.1029) js_child_process_exec_sync returns the stdout string regardless of exit code, and js_child_process_exec_file_sync likewise never throws.

What to do

• On non-zero exit, throw an Error carrying status (exit code), signal, pid, output ([null, stdout, stderr]), stdout, stderr, and cmd.
• The zero-exit path keeps returning stdout (Buffer by default, string with an encoding option).

Compat note: this changes today's lenient behavior (always returns stdout), so existing Perry programs that call execSync on commands that can fail without try/catch will start throwing — matching Node, but worth flagging at merge. Pairs with the exec error-shape and encoding issues.

Parent: #1780. perry 0.5.1029.