feat(icom): the ATU can be taken out of line

TUNE (1C 01 02) started a cycle; nothing sent the 0 that puts the tuner back
through. An ATU chip beside SPLIT now toggles it, and the tuner state is read
on the slow front-panel beat so the radio's own TUNER button stays in sync.

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, IcomConsolePTT,
+  IcomSetRFPower, IcomSetMicGain, IcomSetSplit, IcomTune, IcomSetATU, IcomConsolePTT,
   GetCATState, SetCATFrequency, SetCATMode,
   IcomSetRIT, IcomSetRITOn, IcomSetXITOn,
   IcomSetAntenna, IcomSetPBTInner, IcomSetPBTOuter, IcomSetManualNotch, IcomSetNotchPos,
@@ -20,7 +20,7 @@ import { ShiftRow } from '@/components/ShiftRow';
 
 type IcomState = {
   available: boolean; model?: string; mode?: string;
-  transmitting: boolean; split: boolean; sub_hz?: number;
+  transmitting: boolean; split: boolean; sub_hz?: number; atu_on?: boolean;
   s_meter: number; power_meter: number; swr_meter: number;
   rf_power: number; mic_gain: number;
   af_gain: number; rf_gain: number;
@@ -585,6 +585,9 @@ export function IcomPanel({ onReportRST, isNetwork = false }: { onReportRST?: (r
             {tx ? 'TX ON' : 'MOX'}
           </button>
           <Chip label="SPLIT" on={st.split} onClick={() => set({ split: !st.split }, () => IcomSetSplit(!st.split))} />
+          {/* Tuner IN/OUT — TUNE below starts a cycle but could never take the
+              tuner back out of line. */}
+          <Chip label="ATU" on={!!st.atu_on} onClick={() => set({ atu_on: !st.atu_on } as any, () => IcomSetATU(!st.atu_on))} />
           <button type="button" onClick={tune} disabled={tuning}
             className={cn('w-14 shrink-0 px-2 py-1.5 rounded-md text-[11px] font-bold border transition-colors',
               tuning ? 'bg-warning border-warning text-warning-foreground animate-pulse' : 'bg-card text-foreground border-border hover:bg-muted')}>