BlueZ fills Device1.RSSI only while scanning; sensors connect to us, so
the field stayed empty. MGMT_OP_GET_CONN_INFO (like btmgmt conn-info)
returns the link RSSI; polled per connected sensor and after each write.
Needs CAP_NET_ADMIN (AmbientCapabilities in the collector unit).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
