Review noted the handler's comment said "EPIPE" while the code swallowed every
stdin 'error'. Swallowing any stdin-write error IS correct here — the write is
best-effort and the command's authoritative outcome is its exit code + captured
output (reported by the `close` handler regardless of whether the write landed).
A rare non-EPIPE pipe fault means the command ran with incomplete stdin, which
it surfaces itself via its own exit/output; rejecting `done` would instead
discard that real output and turn it into an opaque infrastructure error. Widen
the comment to state this rather than implying only EPIPE is caught. No behavior
change.