feat(icom): PTT and offset split at the operator's hand

The MOX and SPLIT controls lived at the bottom of the Transmit card, below
the fold on most layouts — a console whose PTT needs scrolling is not a
console. A strip under the mode row now carries the PTT and Split as
OFF/+1k/+5k/+10k, DXpedition style, on a new SetIcomSplitOffset that takes
the chosen TX offset (0 keeps the old CW/SSB convention). The mode-alignment
from the previous fix rides along on every engage.

frontend/src/components/IcomPanel.tsx

@@ -5,7 +5,7 @@ import {
   IcomSetAFGain, IcomSetRFGain, IcomSetNB, IcomSetNBLevel, IcomSetNR, IcomSetNRLevel,
   IcomSetANF, IcomSetAPF, IcomSetAGC, IcomSetPreamp, IcomSetAtt, IcomSetFilter,
   AudioMonitorActive, AudioStartMonitor, AudioStopMonitor,
-  IcomSetRFPower, IcomSetMicGain, IcomSetSplit, IcomTune, IcomSetPTT,
+  IcomSetRFPower, IcomSetMicGain, IcomSetSplit, IcomSetSplitOffset, IcomTune, IcomSetPTT,
   IcomSetScope, IcomScopeData, IcomSetScopeMode, IcomSetScopeEdges, GetCATState, SetCATFrequency, SetCATMode,
   IcomSetRIT, IcomSetRITOn, IcomSetXITOn,
   IcomSetAntenna, IcomSetPBTInner, IcomSetPBTOuter, IcomSetManualNotch, IcomSetNotchPos,
@@ -786,6 +786,29 @@ export function IcomPanel({ onReportRST, isNetwork = false }: { onReportRST?: (r
             );
           })}
         </div>
+        {/* PTT + split, at the operator's hand under the dial — the Transmit
+            card lower down kept these below the fold, and a console whose PTT
+            needs scrolling is not a console. */}
+        <div className="flex items-center gap-1.5 border-t border-border/60 px-2 py-1.5">
+          <button type="button" onClick={toggleMox}
+            className={cn('flex-1 px-3 py-1.5 rounded-md text-xs font-black tracking-wider border transition-colors',
+              tx ? 'bg-destructive border-destructive text-destructive-foreground animate-pulse' : 'bg-card text-foreground border-border hover:bg-muted')}>
+            {tx ? 'TX ON' : 'PTT'}
+          </button>
+          <span className="text-[10px] font-bold uppercase tracking-wider text-muted-foreground pl-1">Split</span>
+          <button type="button" onClick={() => set({ split: false }, () => IcomSetSplit(false))}
+            className={cn('px-2 py-1.5 rounded-md text-[11px] font-bold border transition-colors',
+              !st.split ? 'bg-primary text-primary-foreground border-primary' : 'bg-card text-muted-foreground border-border hover:bg-muted')}>
+            OFF
+          </button>
+          {[1, 5, 10].map((k) => (
+            <button key={k} type="button" onClick={() => set({ split: true }, () => IcomSetSplitOffset(k * 1000))}
+              className={cn('px-2 py-1.5 rounded-md text-[11px] font-bold border transition-colors',
+                st.split ? 'bg-card text-foreground border-border hover:bg-muted' : 'bg-card text-muted-foreground border-border hover:bg-muted')}>
+              +{k}k
+            </button>
+          ))}
+        </div>
       </div>
 
       {/* Live meters — always visible: S (RX, click → RST), Po in watts, SWR. */}