fix: OmniRig reads VFO A first (FreqA→Freq fallback), fixing IC-7610 CAT

The 7610-only FreqA gate broke CAT on the 7610 when FreqA was momentarily 0.
Match DXHunter/WSJT-X: read FreqA first for all rigs, fall back to the generic
Freq (IC-9100 etc.), then FreqB. OmniRig's generic Freq maps to VFO B on the
7610, which is why keying off FreqA is correct.

internal/cat/omnirig.go

@@ -87,14 +87,6 @@ func (o *OmniRig) Connect() error {
 	return nil
 }
 
-// isIC7610 reports whether the connected rig is an IC-7610. OmniRig's generic
-// Freq property reads the wrong VFO on the 7610 (its Main/Sub model confuses the
-// stock ini), so we read VFO A explicitly for it instead — matching what Log4OM
-// shows.
-func (o *OmniRig) isIC7610() bool {
-	return strings.Contains(strings.ToUpper(o.rigType), "7610")
-}
-
 func (o *OmniRig) Disconnect() {
 	if o.rig != nil {
 		o.rig.Release()
@@ -204,23 +196,20 @@ func (o *OmniRig) ReadState() (RigState, error) {
 			s.FreqHz, s.RxFreqHz = freqB, freqA
 		}
 	} else {
-		// Simplex: the operating frequency is OmniRig's generic Freq (the active
-		// VFO), like Log4OM. Fall back to the per-VFO value only if Freq is 0.
+		// Simplex: read VFO A first, fall back to the generic Freq — exactly like
+		// DXHunter/WSJT-X. PM_FREQA rigs (Yaesu, Kenwood) populate FreqA; some
+		// Icoms (IC-9100 etc.) only populate the generic Freq. On the IC-7610
+		// OmniRig's generic Freq reports VFO B (its Main/Sub model confuses the
+		// stock ini), so keying off FreqA gives the operator the VFO they expect.
 		s.Split = false
 		s.RxFreqHz = 0
-		s.FreqHz = freqMain
-		// IC-7610 quirk: OmniRig's generic Freq reports VFO B (its Main/Sub model
-		// confuses the stock ini), so OpsLog showed the wrong VFO. Read VFO A
-		// explicitly for the 7610 — what the operator actually wants to see.
-		if o.isIC7610() && freqA != 0 {
+		switch {
+		case freqA != 0:
 			s.FreqHz = freqA
-		}
-		if s.FreqHz == 0 {
-			if s.Vfo == "B" || s.Vfo == "BB" {
-				s.FreqHz = freqB
-			} else {
-				s.FreqHz = freqA
-			}
+		case freqMain != 0:
+			s.FreqHz = freqMain
+		default:
+			s.FreqHz = freqB
 		}
 	}
 	return s, nil