fix: Yaesu mode commands always addressed the main receiver

Reported, and reasoned out from the half that already worked: a spot click now
tunes the right VFO, but it set the mode with MD0 — main — whatever VFO the
operator was on. Working from SUB, the spot changed the mode of the VFO NOT in
use and left the one in use as it was. The author inferred the sub half from
seeing main change, and was right.

The read had the same fault, so the console displayed main's mode while showing
the sub VFO's frequency.

Mode now addresses the receiver in use — MD0 for main, MD1 for sub — in the poll
read, in SetMode, and in the console's raw-mode setter. A rig without a sub
receiver never sees MD1: curVFO only becomes B where the rig reports its receive
VFO in the first place.

internal/cat/yaesu_panel.go

@@ -430,7 +430,9 @@ func (y *Yaesu) SetYaesuModeRaw(name string) error {
 	if !ok {
 		return fmt.Errorf("yaesu: unknown rig mode %q", name)
 	}
-	return y.setAndRefresh(fmt.Sprintf("MD0%c;", d))
+	// Same receiver as everywhere else — the console must not set main's mode
+	// while the operator is working the sub VFO.
+	return y.setAndRefresh(fmt.Sprintf("MD%s%c;", y.modeVFOSuffix(), d))
 }
 
 // yaesuRawModeDigit maps a rig-mode name to its MD digit.