fix: IC-7610 VFO A over OmniRig + faster Icom LAN reconnect

OmniRig: on the IC-7610 the generic Freq property reports the wrong VFO (its
Main/Sub model confuses the stock ini), so OpsLog showed VFO B. Detect the rig
by RigType and, in simplex, read VFO A explicitly — matching Log4OM. Only the
7610 is affected; other rigs keep using the generic Freq.

Icom network: when the rig tears the session down (control/CI-V 0x05) OpsLog
only logged it and kept the half-dead link until the 6 s liveness timeout
expired. Mark the link dead on 0x05 so Alive() fails on the next poll and the
manager reconnects cleanly right away.

internal/cat/icomnet.go

@@ -136,6 +136,11 @@ type icomNet struct {
 	// but link fine" (stay connected) from "link dead" (reconnect). See Alive().
 	lastRx atomic.Int64
 
+	// dead is set when the rig explicitly tears the session down (control 0x05):
+	// Alive() then returns false immediately so ReadState fails on the next poll and
+	// the manager reconnects cleanly, instead of waiting out the 6 s lastRx timeout.
+	dead atomic.Bool
+
 	// audio is the optional RX audio stream (UDP 50003). nil when audio is off.
 	// Torn down alongside the CI-V/control streams in Close.
 	audio *icomAudio
@@ -178,6 +183,9 @@ func (n *icomNet) markRx() { n.lastRx.Store(time.Now().UnixNano()) }
 // the radio — is gone. Independent of CI-V replies, so a powered-off rig still
 // reads as Alive and the session isn't torn down. Satisfies aliveTransport.
 func (n *icomNet) Alive() bool {
+	if n.dead.Load() {
+		return false // rig sent an explicit disconnect — reconnect now, don't wait
+	}
 	last := n.lastRx.Load()
 	if last == 0 {
 		return true // just connected, nothing received yet — give it a chance
@@ -292,6 +300,7 @@ func (n *icomNet) ctrlPump() {
 					n.ctrlResend(icnLE.Uint16(buf[6:]))
 				}
 			case 0x05: // rig-initiated disconnect — it dropped US
+				n.dead.Store(true) // make Alive() fail now → prompt clean reconnect
 				debugLog.Printf("icom net: rig sent DISCONNECT on control stream — session dropped by the rig")
 			default:
 				// Anything else on the control stream is (almost always) the rig's
@@ -367,6 +376,7 @@ func (n *icomNet) civPump() {
 					n.resend(icnLE.Uint16(buf[6:]))
 				}
 			case typ == 0x05: // rig-initiated disconnect — it dropped US
+				n.dead.Store(true) // make Alive() fail now → prompt clean reconnect
 				debugLog.Printf("icom net: rig sent DISCONNECT on CI-V stream — session dropped by the rig")
 			case typ == 0x00 && k > 0x15 && buf[0x10] == 0xc1: // CI-V data
 				n.trackRxSeq(icnLE.Uint16(buf[6:])) // note gaps for retransmit