Review catch on #700: the inline chain switched to /etc/mosaic/
credentials.json unconditionally when the HOME file was absent, even if
/etc was also absent — diverging from _lib/credentials.sh, which keeps
the $HOME default when neither candidate exists. The /etc switch is now
guarded by existence, restoring lib/inline parity.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01RMoEx7hfdFGjUiCHuN1RRi