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/App.tsx

@@ -38,7 +38,7 @@ import {
   ListCountries,
   GetWinkeyerSettings, SaveWinkeyerSettings, ListSerialPorts, GetWinkeyerStatus,
   WinkeyerConnect, WinkeyerDisconnect, WinkeyerSend, WinkeyerStop, WinkeyerSetSpeed, WinkeyerBackspace,
-  IcomSendCW, IcomStopCW, IcomSetKeySpeed, IcomSetBreakIn, GetIcomState,
+  IcomSendCW, YaesuSendCW, YaesuStopCW, IcomStopCW, IcomSetKeySpeed, IcomSetBreakIn, GetIcomState,
   FlexSendCW, FlexStopCW, FlexSetKeySpeed, FlexBackspaceCW,
   GetDVKMessages, GetDVKStatus, DVKPlay, DVKStop,
   StartCWDecoder, StopCWDecoder, SetCWDecoderPitch,
@@ -965,7 +965,7 @@ export default function App() {
   // CI-V 0x17 (no extra hardware — sends over the CAT connection). Macros,
   // auto-call and <LOGQSO> are shared; only the transport differs.
   const [wkEngine, setWkEngine] = useState<string>('winkeyer');
-  const cwSource: 'winkeyer' | 'icom' | 'flex' = wkEngine === 'icom' ? 'icom' : wkEngine === 'flex' ? 'flex' : 'winkeyer';
+  const cwSource: 'winkeyer' | 'icom' | 'flex' | 'yaesu' = wkEngine === 'icom' ? 'icom' : wkEngine === 'flex' ? 'flex' : wkEngine === 'yaesu' ? 'yaesu' : 'winkeyer';
   const cwSourceRef = useRef(cwSource);
   useEffect(() => { cwSourceRef.current = cwSource; }, [cwSource]);
   // CW break-in (0=OFF, 1=SEMI, 2=FULL) — must be on for the rig's 0x17 keyer to
@@ -1001,6 +1001,7 @@ export default function App() {
   useEffect(() => {
     const connected = cwSource === 'icom' ? (catState.backend === 'icom' && catState.connected)
       : cwSource === 'flex' ? (catState.backend === 'flex' && catState.connected)
+      : cwSource === 'yaesu' ? (catState.backend === 'yaesu' && catState.connected)
       : wkStatus.connected;
     wkActiveRef.current = wkEnabled && connected;
   }, [wkEnabled, wkStatus.connected, cwSource, catState.backend, catState.connected]);
@@ -2558,7 +2559,7 @@ export default function App() {
         // current WPM, so it scales automatically.
         const keyed = resolved + ' ';
         setWkSent(resolved);
-        const sendFn = cwSourceRef.current === 'flex' ? FlexSendCW : cwSourceRef.current === 'icom' ? IcomSendCW : null;
+        const sendFn = cwSourceRef.current === 'flex' ? FlexSendCW : cwSourceRef.current === 'icom' ? IcomSendCW : cwSourceRef.current === 'yaesu' ? YaesuSendCW : null;
         if (sendFn) await sendFn(keyed).catch((e) => setError(String(e?.message ?? e)));
         else await WinkeyerSend(keyed).catch((e) => setError(String(e?.message ?? e)));
         // Only WAIT for the CW to finish on the FINAL segment — auto-call needs the
@@ -2591,6 +2592,7 @@ export default function App() {
     wkSendGenRef.current++; // cancel any in-flight macro send (and its pending <LOGQSO> log)
     if (cwSourceRef.current === 'icom') IcomStopCW().catch(() => {});
     else if (cwSourceRef.current === 'flex') FlexStopCW().catch(() => {});
+    else if (cwSourceRef.current === 'yaesu') YaesuStopCW().catch(() => {});
     else WinkeyerStop().catch(() => {});
   }
   // runAutoCall sends macro i, waits for the keyer to finish, waits the chosen
@@ -3495,6 +3497,7 @@ export default function App() {
           stopAutoCall();
           wkSendGenRef.current++; // abort an in-flight macro send so a pending <LOGQSO> won't fire
           if (cwSourceRef.current === 'icom') IcomStopCW().catch(() => {});
+          else if (cwSourceRef.current === 'yaesu') YaesuStopCW().catch(() => {});
           else if (cwSourceRef.current === 'flex') FlexStopCW().catch(() => {});
           else WinkeyerStop().catch(() => {});
         }