Adds a per-rig meter broadcast channel on RigHandle and threads it
through run_rig_task. SDR meter tick drops from 100 ms to 33 ms; every
tick publishes a MeterUpdate while RigState is only updated on
>=0.25 dB deltas so rigctl/JSON-TCP frontends keep working without
amplifying state churn. Listener handles SubscribeMeter by converting
the TCP connection into a one-way JSON-line stream; TCP_NODELAY is
enabled on every accepted socket for low-latency frame delivery.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
Signed-off-by: Stan Grams <sjg@haxx.space>
sjg
b12d93fb3c
