fix(catshare): echo PTT state so JTDX doesn't drop transmit

JTDX polls get_ptt DURING transmit to confirm the rig is keyed (WSJT-X does not,
which is why it worked and JTDX cut after ~2 s). We answered a blanket "0" (RX),
so JTDX concluded PTT had failed and dropped the over. get_ptt now echoes the
last PTT state commanded via set_ptt — always consistent with the client's own
command. Trace showed T 1 → three t→"0" polls → T 0.

internal/rigctld/rigctld.go

@@ -36,6 +36,7 @@ import (
 	"strconv"
 	"strings"
 	"sync"
+	"sync/atomic"
 	"time"
 )
 
@@ -59,6 +60,13 @@ type Server struct {
 	ln     net.Listener
 	conns  map[net.Conn]struct{}
 	closed bool
+
+	// ptt mirrors the last PTT state a client commanded via set_ptt. WSJT-X/JTDX
+	// poll get_ptt DURING transmit to confirm the rig is keyed; if get_ptt reads
+	// RX they conclude PTT failed and abort the over after a second or two. We
+	// don't read PTT back from every backend, so echo what the client last set —
+	// always consistent with its own command, and enough to satisfy the check.
+	ptt atomic.Bool
 }
 
 func New(port int, rig Rig, logf func(string, ...any)) *Server {
@@ -228,10 +236,12 @@ func (s *Server) handle(line string) (resp string, quit bool) {
 		return rprt(0), false
 
 	case "t", "\\get_ptt":
-		// We do not read PTT back from every backend, and answering "transmitting"
-		// wrongly would make a client hold off for ever. Reporting RX is the safe
-		// direction: the worst case is a client that transmits when we said it
-		// could, which is what it was going to do anyway.
+		// Echo the last commanded PTT state. WSJT-X/JTDX poll this WHILE
+		// transmitting to confirm the rig is keyed; answering a blanket "0" (RX)
+		// made them decide PTT had failed and abort the over after ~1-2 s.
+		if s.ptt.Load() {
+			return "1\n", false
+		}
 		return "0\n", false
 	case "T", "\\set_ptt":
 		if len(args) < 1 {
@@ -242,6 +252,7 @@ func (s *Server) handle(line string) (resp string, quit bool) {
 			s.log("rigctld: set_ptt %v failed: %v", on, err)
 			return rprt(-9), false
 		}
+		s.ptt.Store(on)
 		return rprt(0), false
 
 	case "v", "\\get_vfo":