fix(tci): subscribe to the radio's meters; fix the new-spot count; explain an SMTP refusal

TCI meters: the S-meter came only from RX_SMETER and the transmit meters from
TX_POWER / TX_SWR — commands ExpertSDR3 does not send. The protocol's answer is
a subscription (RX_SENSORS_ENABLE / TX_SENSORS_ENABLE, §4.4 of the TCI PDF),
after which the radio pushes RX_CHANNEL_SENSORS and TX_SENSORS. Nobody had
asked, so the console's meters sat empty in RX and in TX while everything else
worked.

Cluster: the held-spot counter looked for the row it froze on. A station spotted
again REPLACES its row, so that row vanishes in the ordinary course of things
and the count fell through to 'everything is new' — 4, 5, then 500. Counted by
timestamp now, which survives both the replacement and the ring buffer.

SMTP: '535 5.7.139 basic authentication is disabled' is a policy, not a typo.
The message now says so, and says what actually helps, without claiming a policy
when the server simply rejected the password.

internal/cat/tci.go

@@ -155,6 +155,13 @@ func (t *TCI) Connect() error {
 	t.mu.Unlock()
 	debugLog.Printf("TCI: connected to %s", url)
 	go t.reader(conn)
+	// Ask for the meters. Nothing measures anything until this goes out: the
+	// S-meter, the transmit power and the SWR are all pushed by the radio, and
+	// only to a client that has subscribed. 200 ms is the rate the protocol's own
+	// examples use — fast enough for a needle, slow enough not to flood a socket
+	// that also carries audio.
+	_ = t.send("rx_sensors_enable:true,200;")
+	_ = t.send("tx_sensors_enable:true,200;")
 	if t.spotsEnabled {
 		// Forget what we thought was on the panorama at the same moment the radio
 		// is told to drop it. Kept, the memory would suppress the next spot for

internal/cat/tci_panel.go

@@ -233,6 +233,42 @@ func (t *TCI) handlePanel(name string, get func(int) string, args string) bool {
 		if n, ok := num(get(1)); ok && forRX0() {
 			p.SMeter = n
 		}
+	// The meters of ExpertSDR3. The S-meter used to be read only from RX_SMETER
+	// and the transmit ones from TX_POWER / TX_SWR — commands this radio simply
+	// never sends, which is why the console's meters sat empty on a SunSDR in
+	// both RX and TX while everything else worked.
+	//
+	// The protocol's own answer (TCI Protocol.pdf, §4.4) is a SUBSCRIPTION:
+	//
+	//	RX_SENSORS:<rx>,<dBm>;                       (deprecated in 2.0)
+	//	RX_CHANNEL_SENSORS:<rx>,<channel>,<dBm>;     (its replacement)
+	//	TX_SENSORS:<trx>,<mic dBm>,<power W>,<peak W>,<SWR>;
+	//
+	// none of which arrives until the client asks with RX_SENSORS_ENABLE and
+	// TX_SENSORS_ENABLE — see Connect.
+	case "rx_sensors":
+		if v, err := strconv.ParseFloat(strings.TrimSpace(get(1)), 64); err == nil && forRX0() {
+			p.SMeter = int(v)
+		}
+	case "rx_channel_sensors":
+		// Main channel (A) of receiver 0: the one the console is showing.
+		if v, err := strconv.ParseFloat(strings.TrimSpace(get(2)), 64); err == nil &&
+			get(0) == "0" && get(1) == "0" {
+			p.SMeter = int(v)
+		}
+	case "tx_sensors":
+		if get(0) != "0" {
+			break
+		}
+		// arg3 is RMS power, arg4 the peak. The peak is what a power meter's
+		// needle does on speech; the RMS is what the operator is asked to keep
+		// under the amplifier's limit — so RMS is the number, as elsewhere.
+		if v, err := strconv.ParseFloat(strings.TrimSpace(get(2)), 64); err == nil {
+			p.TXPowerW = v
+		}
+		if v, err := strconv.ParseFloat(strings.TrimSpace(get(4)), 64); err == nil {
+			p.TXSWR = v
+		}
 	case "tune":
 		if forRX0() {
 			p.Tuning = yes(get(1))