feat(cat): per-rig Kenwood/Elecraft data-mode choice (USB / MD6 / keep)

No single Kenwood mode digit fits every rig for a data mode: a K3/K4 wants
DATA (MD6), a TS-590SG/TS-990S data mode is a USB modifier set on the rig,
and MD6 on a plain Kenwood is FSK/RTTY. So the operator now chooses in
Settings → CAT: USB (default), DATA (MD6), or leave the rig's mode unchanged.

Only soundcard/data modes (FT8, PSK, JT…) follow this; RTTY/FSK stays its own
native mode, and voice/CW are untouched (isKenwoodDataMode + test).

frontend/src/components/SettingsModal.tsx

@@ -1136,7 +1136,7 @@ export function SettingsModal({ onClose, onSaved, initialSection, onMainPaneChan
   const [modeDraft, setModeDraft] = useState('');
   const [catCfg, setCatCfg] = useState<CATSettings>({
     enabled: false, backend: 'omnirig', omnirig_rig: 1, omnirig_vfo: '', flex_host: '', flex_port: 4992, flex_spots: false, flex_decode_spots: false, flex_decode_secs: 120,
-    yaesu_port: '', yaesu_baud: 38400, yaesu_low_lines: false, kenwood_low_lines: false, kenwood_port: '', kenwood_baud: 9600, kenwood_host: '', xiegu_port: '', xiegu_baud: 19200, xiegu_addr: 0x70, xiegu_ptt_line: '',
+    yaesu_port: '', yaesu_baud: 38400, yaesu_low_lines: false, kenwood_low_lines: false, kenwood_port: '', kenwood_baud: 9600, kenwood_host: '', kenwood_data_mode: 'usb', xiegu_port: '', xiegu_baud: 19200, xiegu_addr: 0x70, xiegu_ptt_line: '',
     icom_port: '', icom_baud: 115200, icom_addr: 0x98, icom_net_host: '', icom_net_user: '', icom_net_pass: '', icom_net_audio: false,
     tci_host: '', tci_port: 40001, tci_spots: false, poll_ms: 250, delay_ms: 0,
     digital_default: 'FT8', share_enabled: false, share_port: 4532,
@@ -2642,6 +2642,18 @@ export function SettingsModal({ onClose, onSaved, initialSection, onMainPaneChan
                 </label>
                 <span className="text-xs text-muted-foreground">{t('cat.lowerLinesHint')}</span>
               </div>
+              <div className="space-y-1">
+                <Label>{t('cat.kwDataMode')}</Label>
+                <Select value={(catCfg as any).kenwood_data_mode || 'usb'} onValueChange={(v) => setCatCfg((s) => ({ ...s, kenwood_data_mode: v } as any))}>
+                  <SelectTrigger className="h-8"><SelectValue /></SelectTrigger>
+                  <SelectContent>
+                    <SelectItem value="usb">{t('cat.kwDataUsb')}</SelectItem>
+                    <SelectItem value="data">{t('cat.kwDataMd6')}</SelectItem>
+                    <SelectItem value="keep">{t('cat.kwDataKeep')}</SelectItem>
+                  </SelectContent>
+                </Select>
+                <span className="text-xs text-muted-foreground">{t('cat.kwDataHint')}</span>
+              </div>
             </>
             )}
             {catCfg.backend === 'icom' && (

frontend/wailsjs/go/models.ts

@@ -1930,6 +1930,7 @@ export namespace main {
 	    kenwood_host: string;
 	    kenwood_port: string;
 	    kenwood_baud: number;
+	    kenwood_data_mode: string;
 	    yaesu_low_lines: boolean;
 	    kenwood_low_lines: boolean;
 	    icom_port: string;
@@ -1975,6 +1976,7 @@ export namespace main {
 	        this.kenwood_host = source["kenwood_host"];
 	        this.kenwood_port = source["kenwood_port"];
 	        this.kenwood_baud = source["kenwood_baud"];
+	        this.kenwood_data_mode = source["kenwood_data_mode"];
 	        this.yaesu_low_lines = source["yaesu_low_lines"];
 	        this.kenwood_low_lines = source["kenwood_low_lines"];
 	        this.icom_port = source["icom_port"];