fix(tci): a refused PTT is reported instead of vanishing

"PTT via CAT does nothing on TCI." What OpsLog sends is right — trx:0,true; is
the documented command and the same one the reference clients send — so the
command was going out and the radio was discarding it.

ExpertSDR announces transmit permission with TX_ENABLE: on connect, and again
whenever the band changes, "in case transmitter permission was changed" (§4.3).
While it is false the radio simply IGNORES trx. OpsLog never read that command,
so there was nothing in the log, nothing on screen, and a dead key.

Now the permission is tracked and SetPTT refuses out loud, naming where to look:
the frequency must be inside a transmit band and TX enabled in ExpertSDR. The
refusal travels the path that already exists — Manager.SetPTT to pttKey, which
logs it and hands it to the UI.

Silence is not a "no". A radio that never mentions TX_ENABLE — an older
ExpertSDR, or another program speaking TCI — is not treated as refusing: we key
and let it decide. Permission is also forgotten on connect, so a refusal
remembered from a band since left cannot block PTT until a restart.

This may not be the operator's own cause, and that is the other half of the
change: if it is not, the log now settles it in one line. cat: TCI: → trx:0,true;
present means the command left OpsLog and the radio ignored it for a reason it
has not told us; absent means the fault is on this side.

changelog.json

@@ -5,12 +5,14 @@
     "en": [
       "An entity that is a single island group now fills the IOTA reference on its own — no callbook subscription needed.",
       "CAT sharing can now speak TCI instead of Hamlib, so a TCI-only program reaches whatever radio OpsLog is on.",
-      "Lookup cache: a TTL of 0 switches it off, so a callbook record you are correcting is re-read every time."
+      "Lookup cache: a TTL of 0 switches it off, so a callbook record you are correcting is re-read every time.",
+      "TCI: when the radio forbids transmitting, PTT now says so instead of doing nothing silently."
     ],
     "fr": [
       "Une entité qui est un seul groupe d’îles remplit désormais la référence IOTA toute seule, sans abonnement callbook.",
       "Le partage CAT peut désormais parler TCI au lieu de Hamlib : un logiciel TCI atteint la radio, quelle qu’elle soit.",
-      "Cache des recherches : un TTL à 0 le désactive, pour relire à chaque fois une fiche callbook en cours de correction."
+      "Cache des recherches : un TTL à 0 le désactive, pour relire à chaque fois une fiche callbook en cours de correction.",
+      "TCI : quand la radio interdit l’émission, le PTT le dit désormais au lieu de ne rien faire en silence."
     ]
   },
   {