fix(icom): power in watts on the 7760, and Listening restarts clean

The power meter applies Icom's own meter calibration (raw 143 = half
deflection, 213 = full scale) anchored against the real radio: a measured
100 W sits at half deflection of the 7760's 250 W face — the linear guess
showed it as 140. The RF power slider says watts on a 200 W rig instead of a
percentage the operator has to convert.

And the Listening button, pressed while a network Icom is connected, restarts
the monitor render-only: it used to open a USB capture from the From-radio
device as well, and that second producer interleaved with the network pushes
chopped the audio to pieces.

frontend/src/components/IcomPanel.tsx

@@ -129,6 +129,19 @@ function fmtVFO(hz?: number): string {
 }
 
 // modeMatches marks a mode button active, folding the rig's USB/LSB into SSB.
+// icomWatts turns the backend's 0-100 meter percentage back into watts on the
+// IC-7760's own meter face. The backend value is linear in the RAW meter byte
+// (0-255 → 0-100), but Icom's calibration is not: raw 143 is half deflection
+// and raw 213 is full scale. On a real 7760 a measured 100 W sits at half
+// deflection of the 250 W face — the linear ×2.5 first tried showed 140 W for
+// it. Below half scale watts run 0→100, above it 100→250.
+function icomWatts(pct: number): { w: number; defl: number } {
+  const raw = Math.max(0, pct * 2.55);
+  const defl = raw <= 143 ? (raw / 143) * 50 : Math.min(100, 50 + ((raw - 143) / 70) * 50);
+  const w = raw <= 143 ? (raw / 143) * 100 : Math.min(250, 100 + ((raw - 143) / 70) * 150);
+  return { w: Math.round(w), defl };
+}
+
 function modeMatches(btn: string, cur?: string): boolean {
   if (!cur) return false;
   if (btn === 'SSB') return cur === 'SSB' || cur === 'USB' || cur === 'LSB';
@@ -743,11 +756,13 @@ export function IcomPanel({ onReportRST, isNetwork = false }: { onReportRST?: (r
             title={onReportRST ? t('rst.clickToFill') : undefined}
             onClick={onReportRST ? () => onReportRST(sMeterRST(sp.s, sp.over, st.mode)) : undefined} />
         ); })()}
-        {/* The meter reads 0-100% of the rig's own scale. On a 100 W rig the
-            percentage IS the watts; the IC-7760's meter runs to 250 W (the rig
-            makes 200), so its percentage is worth 2.5 W a point — same face as
-            the radio's. */}
-        <Meter label="Po" value={st.power_meter} accent="#ef4444" scale={`${Math.round(st.power_meter * (((st.model ?? '').includes('7760')) ? 2.5 : 1))} W`} />
+        {(() => {
+          if ((st.model ?? '').includes('7760')) {
+            const { w, defl } = icomWatts(st.power_meter);
+            return <Meter label="Po" value={defl} accent="#ef4444" scale={`${w} W`} />;
+          }
+          return <Meter label="Po" value={st.power_meter} accent="#ef4444" scale={`${st.power_meter} W`} />;
+        })()}
         <Meter label="SWR" value={st.swr_meter} accent="#f59e0b" scale={st.swr_meter > 0 ? `${(1 + st.swr_meter / 33.3).toFixed(1)}` : '1.0'} />
       </div>
 
@@ -793,7 +808,11 @@ export function IcomPanel({ onReportRST, isNetwork = false }: { onReportRST?: (r
       <Card icon={Mic} title={t('icmp.transmit')} accent="#ef4444">
         <Row label={t('icmp.power')}>
           <Slider value={st.rf_power} accent="#ef4444" onChange={(v) => set({ rf_power: v }, () => IcomSetRFPower(v))} />
-          <span className="w-8 text-right text-xs font-mono tabular-nums text-muted-foreground">{st.rf_power}</span>
+          {/* PC is a percentage of the rig's rated power; on a 200 W rig the
+              operator thinks in watts, so say it in watts there. */}
+          <span className="w-12 text-right text-xs font-mono tabular-nums text-muted-foreground">
+            {(st.model ?? '').includes('7760') ? `${st.rf_power * 2} W` : st.rf_power}
+          </span>
         </Row>
         {isPhone && (
           <Row label={t('icmp.mic')}>