M3 step 5: Sweep, the band's signal strength as bars and a waterfall

Tab in the LoRa Scanner sweeps 863-870 MHz in 100 kHz steps (the
strongest of three RSSI readings at each, at 125 kHz), shown as bars with
peak hold over a waterfall, the Sniffer's frequency marked (Q98). The
Sweep pauses the Sniffer and keeps its packets; Tab resumes it (Q99).
Status Bar: SW. The floor, top and peaks are host-tested; `lora sweep
on|off|dump` prints them on the console.

At the desk: about 607 ms a pass, a flat floor at -100 to -102 dBm
(15 dB above the chip's own) and a steady carrier at 863.2 MHz.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EhqxQ49eCju4CzKYNjZzwT

src/ui/widgets.cpp

@@ -53,6 +53,7 @@ void statusBar(Canvas& c, const StatusInfo& info) {
     switch (info.radio) {  // Q101: muted while listening, bright for a moment on each packet
         case StatusInfo::Radio::Listening: right("L", kMuted); break;
         case StatusInfo::Radio::Packet: right("L", kAccent); break;
+        case StatusInfo::Radio::Sweep: right("SW", kMuted); break;  // the Sniffer is paused
         case StatusInfo::Radio::None: break;
     }
     switch (info.gnss) {  // Q61: muted while searching, normal with a Fix, the count with a 3D Fix