feat(udp): spot clicks switch the decoder's mode

Configure (message 15), mode field only, every other field sent as
no-change: an FT4 spot clicked while WSJT-X sits in FT8 lands the operator
ready to decode instead of staring at gibberish. Sent to every instance
heard this session — one already in the right mode treats it as a no-op —
and only for modes the decoder actually speaks (FT8/FT4/JT65/JT9/MSK144/
Q65/FST4); CW and SSB are none of its business. Toggle in the Connections
panel, on by default.

frontend/wailsjs/go/main/App.d.ts

@@ -142,6 +142,8 @@ export function ComputeQSOAwardRefs(arg1:qso.QSO):Promise<Array<main.QSOAwardRef
 
 export function ComputeStationInfo(arg1:string,arg2:string):Promise<main.StationInfoComputed>;
 
+export function ConfigureDecoderMode(arg1:string):Promise<void>;
+
 export function ConnectAllClusters():Promise<void>;
 
 export function ConnectClusterServer(arg1:number):Promise<void>;
@@ -620,6 +622,8 @@ export function GetWinkeyerStatus():Promise<winkeyer.Status>;
 
 export function GetWorkedCallVariants():Promise<boolean>;
 
+export function GetWsjtFollowMode():Promise<boolean>;
+
 export function GetWsjtHighlight():Promise<boolean>;
 
 export function GetYaesuBandAntennas():Promise<Record<string, number>>;
@@ -1248,6 +1252,8 @@ export function SetWinkeyerTrace(arg1:boolean):Promise<void>;
 
 export function SetWorkedCallVariants(arg1:boolean):Promise<void>;
 
+export function SetWsjtFollowMode(arg1:boolean):Promise<void>;
+
 export function SetWsjtHighlight(arg1:boolean):Promise<void>;
 
 export function SetYaesuAFGain(arg1:number):Promise<void>;