Previously --log-file only set DECNET_LOG_FILE inside containers with no
volume mount, so logs were lost on container restart and never visible on
the host. Now generate_compose binds the host log dir to
/var/log/decnet inside every service container so the file appears on
the host as expected.
- composer.py: _resolve_log_file() maps host path → container path;
generate_compose() mkdir's host dir and injects volume + DECNET_LOG_FILE
- tests/test_log_file_mount.py: 9 new tests covering mount format,
env injection, dir creation, and dedup
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
