Salvages Codex's FreeBSD-validated fix from
fix/jail-spawner-freebsd-command-format, taking ONLY the spawner.rs change onto
current main. (The original branch also re-ran a markdown formatter and would
have re-corrupted the jailed-spawn design doc + README, so those are dropped.)
My merged jail_wrap emitted the ephemeral jail command as two argv tokens
("command", binary), but jail(8) expects a single name=value parameter
(command=<binary>). Without this the `jail -c` ephemeral path fails on FreeBSD.
Fixes the ephemeral builder and the two jail_tests expectations.
Co-authored-by: Sam & Codex (fix/jail-spawner-freebsd-command-format)
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
