The gpg helper runs commands like amend with StreamOutput, so their
output isn't captured and a failed run returns an empty output string;
the index.lock message is carried by the error instead. isRetryableError
only inspects the output, so the retry loop never fires for these
commands. In practice this means a `shift-A` amend issued while a
foreground `git status` refresh briefly holds index.lock fails outright
instead of retrying.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>