feat(icom): phase 5 — the voice keyer plays to the radio over the LAN

The audio session opens its TX side alongside RX (txenable in the conninfo,
16 kHz both ways), the stream gains a paced sender — 320 samples every 20 ms,
the frame mirroring what the rig itself sends on this socket, IDs swapped —
and the network Icom takes the same NetworkPlayer slot a TCI radio does: pick
'Radio (network audio)' as the To-radio device and the voice keyer needs no
cable and no virtual sound card. PTT brackets the message through the same
code as every other audio path.

app.go

@@ -8440,7 +8440,7 @@ func (a *App) ListAudioInputDevices() ([]audio.Device, error) {
 		return devs, err
 	}
 	if a.tciAudioAvailable() {
-		devs = append([]audio.Device{{ID: audio.NetworkDeviceID, Name: "Radio (TCI network audio)"}}, devs...)
+		devs = append([]audio.Device{{ID: audio.NetworkDeviceID, Name: "Radio (network audio)"}}, devs...)
 	}
 	return devs, nil
 }
@@ -8467,7 +8467,7 @@ func (a *App) ListAudioOutputDevices() ([]audio.Device, error) {
 		return devs, err
 	}
 	if audio.NetworkPlayerReady() {
-		devs = append([]audio.Device{{ID: audio.NetworkDeviceID, Name: "Radio (TCI network audio)"}}, devs...)
+		devs = append([]audio.Device{{ID: audio.NetworkDeviceID, Name: "Radio (network audio)"}}, devs...)
 	}
 	return devs, nil
 }
@@ -15625,6 +15625,9 @@ func (a *App) reloadCAT() {
 			}
 		}
 		a.cat.Start(cat.NewIcomNet(s.IcomNetHost, s.IcomNetUser, s.IcomNetPass, s.IcomAddr, s.DigitalDefault, audioSink))
+		// With the audio session open the radio can also TAKE audio: offer it to
+		// the voice keyer, the way a TCI radio is offered.
+		a.installIcomTXPlayer(audioSink != nil)
 	case "tci":
 		// Expert Electronics TCI (WebSocket) — SunSDR / ExpertSDR2, or any
 		// TCI-compatible server. The receive audio rides the same socket, so