feat(winkeyer): K3NG keyers, and wait out their reboot

The operator's keyer is a K3NG — an Arduino running an emulation of the
WinKeyer protocol — which changes the diagnosis and nearly broke it.

Checked against K3NG's own source before anything else, because yesterday's
handshake now FAILS a connect where it used to press on regardless. It is
safe: k3ng_keyer.ino implements admin echo (0x04) and echoes the byte back,
0x13 is a documented no-op, and OPTION_WINKEY_STRICT_HOST_OPEN — on by
default — ignores every byte except 0x00 before host open, so the resync
nulls are dropped harmlessly and the echo probe still gets through.

The real cause is in K3NG's options file, beside the feature itself:
"disabling Automatic Software Reset is highly recommended", and an option
to "discard errant serial port bytes at startup" for when it is not. On an
Arduino, DTR is wired to reset through a capacitor: opening the port reboots
the board into its bootloader. Ours spoke 400 ms later, to a keyer that was
not running yet.

So the retry now waits 2.5 s, which recovers it without an operator pressing
connect twice, and the engine list gains a K3NG entry that skips the doomed
fast attempt altogether. Everything else is identical to a K1EL — same
settings panel, same protocol.

changelog.json

@@ -9,7 +9,7 @@
       "Appearance: new Sahara theme, warm sand tones for long sessions in daylight.",
       "US counties: Connecticut returned the census planning regions, and San Francisco, Doña Ana, Baltimore city and several Alaska boroughs matched nothing at all. The cluster now shows the same county as the Info panel. Re-download the county database.",
       "QSL: the manager (QSL_VIA) and the sending method (QSL_SENT_VIA / QSL_RCVD_VIA) are separate fields at last, as ADIF defines them. Imports keep both, exports write both, and a log where they were mixed is offered a correction at startup.",
-      "WinKeyer: the opening handshake follows K1EL’s own sequence (RTS off, parser resync, echo test), which wakes keyers that stayed silent — and a port where nothing answers now says so instead of showing “connected”."
+      "WinKeyer: the opening handshake follows K1EL’s own sequence (RTS off, parser resync, echo test), which wakes keyers that stayed silent, and a port where nothing answers now says so instead of showing “connected”. K3NG keyers have their own entry in the list — they reboot when the port opens and need longer to answer."
     ],
     "fr": [
       "Amplificateurs : cochez ceux qui partagent un combineur et ON, OFF et OPERATE agissent sur tous à la fois. Chacun garde ses propres mesures.",
@@ -18,7 +18,7 @@
       "Apparence : nouveau thème Sahara, tons sable chauds pour les longues sessions en plein jour.",
       "Comtés US : le Connecticut renvoyait les planning regions du recensement, et San Francisco, Doña Ana, Baltimore city et plusieurs districts d’Alaska ne correspondaient à rien. Le cluster affiche maintenant le même comté que le panneau Info. Rechargez la base des comtés.",
       "QSL : le manager (QSL_VIA) et le mode d’envoi (QSL_SENT_VIA / QSL_RCVD_VIA) sont enfin deux champs distincts, comme le veut l’ADIF. Les imports gardent les deux, les exports les écrivent, et un log où ils étaient mélangés se voit proposer une correction au démarrage.",
-      "WinKeyer : la séquence d’ouverture suit celle de K1EL (RTS bas, resynchronisation, test d’écho), ce qui réveille les manipulateurs muets — et un port où rien ne répond le dit au lieu d’afficher « connecté »."
+      "WinKeyer : la séquence d’ouverture suit celle de K1EL (RTS bas, resynchronisation, test d’écho), ce qui réveille les manipulateurs muets, et un port où rien ne répond le dit au lieu d’afficher « connecté ». Les K3NG ont leur propre entrée dans la liste : ils redémarrent à l’ouverture du port et mettent plus longtemps à répondre."
     ]
   },
   {