fix(icom): say when a radio has no scope stream instead of drawing nothing

The CI-V trace settles it: the IC-7851 answers 27 10 01 with FB and 27 14 00
with its mode, but refuses 27 11 in BOTH shapes — it controls its scope over
CI-V and never streams it. Its last firmware is from 2016, older than the
waveform stream itself; Hamlib's caps claim otherwise, the radio is the
authority.

Rejected both ways is a permanent answer, so it is remembered and reported:
the panadapter says the radio does not send its scope, which is the one thing a
black rectangle could not say.

frontend/src/components/IcomPanel.tsx

@@ -292,6 +292,9 @@ function ScopePanadapter() {
   const wfRef = useRef<HTMLCanvasElement>(null); // waterfall
   const peakRef = useRef(160); // running amplitude ceiling for auto-scale
   const holdRef = useRef<number[]>([]); // per-bin peak-hold line
+  // Some radios control their scope over CI-V but never stream it (IC-7851).
+  // Saying so beats a black rectangle, which reads as a bug in OpsLog.
+  const [unsupported, setUnsupported] = useState(false);
   const spanRef = useRef({ low: 0, high: 0 }); // latest sweep edges, for click-to-tune
   const vfoRef = useRef(0);    // latest VFO frequency, for wheel-tune
   const centerRef = useRef(0); // scope centre we last set (for pan ◀/▶)
@@ -333,6 +336,7 @@ function ScopePanadapter() {
       if (!alive) return;
       try {
         const sw = await IcomScopeData();
+        if (sw?.unsupported) setUnsupported(true);
         if (sw && sw.seq !== lastSeq && sw.amp && sw.amp.length) {
           lastSeq = sw.seq;
           setFixed(sw.fixed);
@@ -543,7 +547,10 @@ function ScopePanadapter() {
           <Chip label={on ? 'ON' : 'OFF'} on={on} onClick={toggle} />
         </div>
       </div>
-      {on && (
+      {on && unsupported && (
+        <div className="px-3 py-2 text-xs text-muted-foreground">{t('icmp.scopeNoStream')}</div>
+      )}
+      {on && !unsupported && (
         <div className="p-3">
           <div className="rounded-xl overflow-hidden ring-1 ring-info/20 shadow-lg shadow-sky-500/5 bg-[#05070e]">
             <canvas ref={canvasRef} onDoubleClick={onDblClick}