feat: CW through the Yaesu keyer — fifth CW engine

The radio has a keyer and a command to feed it (KY), so an FTDX10 needs no
WinKeyer and no second cable, exactly as the Icom CI-V and Flex CWX engines
already do. The rig keys with its own timing, which is why the spacing is right
where a PC keying a line through USB latency drifts.

Text is filtered to what the keyer can actually send: an unsupported byte does
not produce an error on a Yaesu, it can abort the whole buffer, so the rest of a
macro would vanish silently. It is then fed in 24-character pieces, waiting for
room between them — the rig DROPS what does not fit, again with no error, so a
contest CQ would lose its tail.

STOP is the honest gap. Yaesu documents no buffer-clear, so it drops the
transmitter (TX0) instead: nothing queued reaches the air, which is what Escape
means to an operator. It deliberately does NOT send "KY0;" — a plausible-looking
clear that the rig would read as the CHARACTER zero and transmit.

A test caught a real one on the way: tabs and newlines were dropped as
"unsupported", gluing the words either side together, so a macro written on two
lines went out as CQCQ. Whitespace now becomes a word gap before filtering.

Settings warn when the Yaesu keyer is selected without the Yaesu CAT backend —
otherwise it simply never keys, with nothing on screen saying why.

Send path follows the CAT reference and how Hamlib drives these rigs; NOT yet
verified on the air.

frontend/src/components/WinkeyerPanel.tsx

@@ -26,7 +26,7 @@ interface Props {
   wpm: number;
   macros: WKMacro[];
   sent: string; // text echoed back by the keyer as it transmits
-  source: 'winkeyer' | 'icom' | 'flex';      // CW output engine (chosen in Settings → CW Keyer)
+  source: 'winkeyer' | 'icom' | 'flex' | 'yaesu'; // CW output engine (chosen in Settings → CW Keyer)
   breakIn?: number;                          // Icom CW break-in: 0=OFF, 1=SEMI, 2=FULL
   onSetBreakIn?: (mode: number) => void;
   onSelectPort: (p: string) => void;
@@ -101,16 +101,18 @@ export function WinkeyerPanel({
         <Radio className="size-4 text-primary shrink-0" />
         {/* CW output engine (chosen in Settings → CW Keyer). */}
         <span className="text-xs font-semibold uppercase tracking-wider text-muted-foreground shrink-0">
-          {source === 'icom' ? 'Icom CW' : source === 'flex' ? 'Flex CWX' : 'WinKeyer'}
+          {source === 'icom' ? 'Icom CW' : source === 'flex' ? 'Flex CWX' : source === 'yaesu' ? 'Yaesu CW' : 'WinKeyer'}
         </span>
         <span className={cn('size-2 rounded-full', connected ? (status.busy ? 'bg-warning animate-pulse' : 'bg-success') : 'bg-muted-foreground/40')}
           title={connected ? (status.busy ? t('wkp.sending') : t('wkp.connectedV', { version: status.version })) : t('wkp.disconnected')} />
         <div className="flex-1" />
-        {source === 'icom' || source === 'flex' ? (
+        {source === 'icom' || source === 'flex' || source === 'yaesu' ? (
           <span className="text-[11px] font-medium text-muted-foreground">
             {source === 'flex'
               ? (connected ? t('wkp.cwxReady') : t('wkp.cwxOffline'))
-              : (connected ? t('wkp.civReady') : t('wkp.civOffline'))}
+              : source === 'yaesu'
+                ? (connected ? t('wkp.rigReady') : t('wkp.rigOffline'))
+                : (connected ? t('wkp.civReady') : t('wkp.civOffline'))}
           </span>
         ) : !connected ? (
           <>