feat: share the CAT link with other programs (Hamlib NET rigctl server)

A native CAT backend owns the rig's serial port, and Windows gives a COM port to
one process — so choosing native CAT locked WSJT-X, MSHV and JTDX out of the
radio entirely. That is the cost of dropping OmniRig, which was itself a sharing
layer, and it has to be paid back.

OpsLog now becomes the server, as wfview does. It speaks the Hamlib net rigctl
protocol, which every one of those programs supports natively (rig model "Hamlib
NET rigctl", 127.0.0.1:4532) with no driver to install. It sits in front of the
MANAGER, not a backend, so an operator on OmniRig, Flex, Icom or TCI gets the
same server.

Two details that decide whether a client works at all rather than degrading:
dump_state is parsed positionally and WSJT-X refuses to proceed without a
well-formed block, so it is written out in full and its shape is pinned by a
test; and set_vfo / set_split_vfo answer RPRT 0 rather than an error, because
OpsLog follows the rig's own VFO and a refusal makes WSJT-X abandon the
connection. Unknown commands answer RPRT -11 — never silence, which hangs a
client instead.

The whole protocol is tested against a fake rig, plus one end-to-end exchange
over a real socket, since the framing is as much the contract as the text.

Also: the Yaesu backend is confirmed working on a real FTDX10 (frequency, mode,
VFO, split), so its "not yet verified" note is now wrong and is corrected.

changelog.json

@@ -3,6 +3,7 @@
     "version": "0.21.9",
     "date": "2026-07-28",
     "en": [
+      "CAT sharing: OpsLog can now serve its rig connection to other programs (Settings → CAT → Share CAT). WSJT-X, JTDX, MSHV or Log4OM connect with rig model \"Hamlib NET rigctl\" at 127.0.0.1:4532 — needed because a native CAT backend holds the radio serial port on its own. Works with every backend.",
       "Native Yaesu CAT: a new backend talks to an FTDX10/FTDX101 directly over its serial port, without OmniRig — frequency, mode, VFO A/B, split and PTT. Pick \"Yaesu (native CAT)\" in Settings → CAT. First release, feedback welcome.",
       "Changing band from OpsLog now updates the displayed frequency straight away. The rig moved, but its answer arrived inside the short grace window that protects what you are typing and was discarded — so the frequency stayed on the old band until you nudged the VFO.",
       "Bulk edit can now set the contacted station gridsquare, so a batch of QSOs imported without a locator can be corrected in one go.",
@@ -13,6 +14,7 @@
       "CQ and ITU zones you correct by hand in your profile stay corrected. They are derived from cty.dat, which gives the zones of the whole entity — in a country spanning several, the automatic value is wrong and it came back at every restart. They now only fill in when empty, and recompute when the callsign or grid changes."
     ],
     "fr": [
+      "Partage du CAT : OpsLog peut désormais servir sa liaison radio aux autres logiciels (Réglages → CAT → Partager le CAT). WSJT-X, JTDX, MSHV ou Log4OM s'y connectent avec le modèle « Hamlib NET rigctl » sur 127.0.0.1:4532 — nécessaire car un backend CAT natif occupe seul le port série. Fonctionne avec tous les backends.",
       "CAT Yaesu natif : un nouveau backend dialogue directement avec un FTDX10/FTDX101 par son port série, sans OmniRig — fréquence, mode, VFO A/B, split et PTT. À choisir dans Réglages → CAT sous « Yaesu (CAT natif) ». Première version, retours bienvenus.",
       "Changer de bande depuis OpsLog met désormais la fréquence affichée à jour immédiatement. La radio se déplaçait bien, mais sa réponse arrivait pendant le court délai qui protège votre saisie et était ignorée — la fréquence restait donc sur l'ancienne bande jusqu'à ce qu'on touche le VFO.",
       "L'édition groupée peut désormais définir le locator de la station contactée : un lot de QSO importés sans locator se corrige en une fois.",