Bring up the two-Pluto link and decode a first burst

[AbdullahAlNafisah]

Both Plutos are connected and identified by serial, firmware v0.39. Nothing has transmitted yet.

Next, on the ota-two-device branch:

1. Run python -m nsm.sdr.pluto with both boards attached. It configures them and sends a short test burst at 850 MHz, so check the antennas first.
2. Send one burst from the TX board, capture it on the RX board, decode it, and check the bits match. Keep the session record.

Once that works, the merge gate in #1 is met and the physical Eb/N0 sweep can start.