fix(tci): pick the sideband from the frequency just commanded

Clicking a spot sets the frequency, then the mode 150 ms later, and SetMode
chose USB or LSB from t.freqA — the frequency the radio had ECHOED. From 7 MHz
onto a 14 MHz spot that echo has often not landed, so the sideband was computed
for the band being left: LSB on 20 m. Clicking the same spot again, the echo
having arrived, gave USB. Reported from a SunSDR as 'the frequency is right, the
mode is wrong until I click twice'.

SetFrequency now records what was asked for and SetMode prefers it until the
radio's own echo confirms the move.

The server's 'protocol:' announcement is also kept instead of being filed under
unhandled: it names the ExpertSDR and its TCI version, and panorama spots need
TCI 1.5 — older servers accept the spot commands and silently drop them, which
is indistinguishable from a broken logger. Now it says so.

internal/cat/tci.go

@@ -27,6 +27,12 @@ type TCI struct {
 
 	digitalDefault string // surfaced when the rig reports a digital mode (FT8/…)
 	spotsEnabled   bool   // mirror cluster spots onto the TCI panorama
+	// wantFreq is the frequency last COMMANDED and not yet echoed back, used to
+	// pick the sideband before the radio has confirmed the move.
+	wantFreq int64
+	// What the server said it is, from its "protocol:" announcement.
+	serverName    string
+	serverVersion string
 
 	// OnSpotClick is called when the user clicks one of our spots on the TCI
 	// panorama (callsign + freq), so the host can fill the entry form. Set before
@@ -334,6 +340,11 @@ func (t *TCI) ReadState() (RigState, error) {
 
 // SetFrequency tunes VFO A (the main/RX VFO).
 func (t *TCI) SetFrequency(hz int64) error {
+	// Remember what we ASKED for. SetMode reads it to choose the sideband, and
+	// the radio's own echo can be a moment behind — see SetMode.
+	t.mu.Lock()
+	t.wantFreq = hz
+	t.mu.Unlock()
 	return t.send(fmt.Sprintf("vfo:0,0,%d;", hz))
 }
 
@@ -342,6 +353,17 @@ func (t *TCI) SetFrequency(hz int64) error {
 func (t *TCI) SetMode(mode string) error {
 	t.mu.Lock()
 	freq := t.freqA
+	// Prefer the frequency we just COMMANDED over the one the radio has echoed.
+	//
+	// Clicking a spot sets the frequency and then the mode, and the sideband is
+	// chosen from the frequency (below 10 MHz → LSB). Read from the echo, that
+	// is the frequency we were on BEFORE the click whenever the echo has not
+	// landed yet: a 14 MHz spot clicked from 7 MHz got LSB, and clicking the same
+	// spot again — now that the echo has arrived — got USB. Reported from a
+	// SunSDR as "the frequency is right, the mode is wrong until I click twice".
+	if t.wantFreq > 0 {
+		freq = t.wantFreq
+	}
 	t.mu.Unlock()
 	m := adifToTCIMode(mode, freq)
 	if m == "" {
@@ -493,6 +515,18 @@ func (t *TCI) handle(msg string) {
 	switch lower {
 	case "device":
 		t.device = strings.TrimSpace(args)
+	// The server's own announcement: "protocol:ExpertSDR3,1.9;" — its name and
+	// the TCI version it speaks. Worth keeping rather than filing under
+	// "unhandled": panorama spots need a version that HAS the spot command, and
+	// without this an operator on an older ExpertSDR sees nothing on the
+	// waterfall and nothing anywhere saying why.
+	case "protocol":
+		t.serverName, t.serverVersion = get(0), get(1)
+		debugLog.Printf("TCI: server is %s, TCI %s", t.serverName, t.serverVersion)
+		if t.spotsEnabled && tciSpotsUnsupported(t.serverVersion) {
+			debugLog.Printf("TCI: this server speaks TCI %s — panorama spots need 1.5 or later, so they will not appear",
+				t.serverVersion)
+		}
 	// The radio ANNOUNCES its audio format at connect —
 	// "audio_stream_sample_type:float32" and "audio_stream_channels:2" — which
 	// is better evidence than anything derived from a frame, and it arrives
@@ -516,6 +550,10 @@ func (t *TCI) handle(msg string) {
 				switch get(1) {
 				case "0":
 					t.freqA = hz
+					// The radio has caught up: from here the echo IS the truth.
+					if t.wantFreq != 0 && absInt64(hz-t.wantFreq) < 100 {
+						t.wantFreq = 0
+					}
 				case "1":
 					t.freqB = hz
 				}
@@ -651,3 +689,18 @@ func adifToTCIMode(mode string, freqHz int64) string {
 		return "digu"
 	}
 }
+
+// tciSpotsUnsupported reports whether a TCI version predates the spot commands.
+//
+// SPOT / SPOT_DELETE / SPOT_CLEAR arrived in TCI 1.5. An older ExpertSDR accepts
+// the connection, answers frequency and mode perfectly, and silently ignores
+// every spot — which is indistinguishable from a bug in the logger unless
+// somebody says so. Anything unparseable is treated as supported: refusing to
+// draw on a doubt would be the worse mistake.
+func tciSpotsUnsupported(version string) bool {
+	var maj, min int
+	if n, err := fmt.Sscanf(strings.TrimSpace(version), "%d.%d", &maj, &min); n < 2 || err != nil {
+		return false
+	}
+	return maj < 1 || (maj == 1 && min < 5)
+}

internal/cat/tci_test.go

@@ -0,0 +1,24 @@
+package cat
+
+import "testing"
+
+func TestTCISpotsUnsupported(t *testing.T) {
+	// SPOT arrived in TCI 1.5. The SunSDR2 PRO report that prompted this was an
+	// ExpertSDR announcing 1.3 — spots accepted and silently dropped.
+	for _, c := range []struct {
+		version string
+		old     bool
+	}{
+		{"1.3", true},
+		{"1.4", true},
+		{"1.5", false},
+		{"1.9", false},
+		{"2.0", false},
+		{"", false},      // unparseable → assume it works
+		{"weird", false}, // refusing to draw on a doubt is the worse mistake
+	} {
+		if got := tciSpotsUnsupported(c.version); got != c.old {
+			t.Errorf("tciSpotsUnsupported(%q) = %v, want %v", c.version, got, c.old)
+		}
+	}
+}