NATS_URL=                    # empty = stdout fallback
MCAP_DIR=/data/mcap
POLL_INTERVAL_S=30
LOG_LEVEL=INFO
# thresholds (optional, defaults in code)
BATTERY_LOW_V=13.5
USBL_SNR_LOW=5.0
USBL_DIST_SPIKE_M=50
WATCHDOG_IMU_S=2.0