fix(tci): send the spot colour as an unsigned ARGB integer

Expert Electronics' own document gives the command whole:

    SPOT:RN6LHF,CW,7100000,16711680,ANY_TEXT;

16711680 is 0x00FF0000 — positive. This backend sent the same field as a SIGNED
32-bit value, from a third-party example: with the alpha byte set to FF for
opacity, 0xFFFFA500 becomes -22336, and a spot whose colour ExpertSDR cannot
read is dropped without a reply or an error.

Reported on ExpertSDR3 1.3, which speaks TCI 2.x — the protocol version was
never the problem, and my first reading of that report was wrong.

The first three spots are now logged verbatim: an ignored spot leaves no trace
whatsoever, so that line is the only evidence of what went out.

internal/cat/tci.go

@@ -33,6 +33,8 @@ type TCI struct {
 	// What the server said it is, from its "protocol:" announcement.
 	serverName    string
 	serverVersion string
+	// How many spots have been logged verbatim (the first few only).
+	spotsSent int
 
 	// 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
@@ -160,6 +162,9 @@ func (t *TCI) Connect() error {
 	// 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.
+	if t.spotsEnabled {
+		debugLog.Printf("TCI: panorama spots are ON — spots will be sent to the radio")
+	}
 	_ = t.send("rx_sensors_enable:true,200;")
 	_ = t.send("tx_sensors_enable:true,200;")
 	if t.spotsEnabled {
@@ -241,11 +246,19 @@ func (t *TCI) SendSpot(s SpotInfo) error {
 		// other two matching what already works here.
 		_ = t.send(fmt.Sprintf("spot_delete:%s;", call))
 	}
-	// TCI's SPOT command wants the colour as a signed 32-bit DECIMAL integer in
-	// 0xAARRGGBB order — NOT a "0x…" hex string (e.g. "spot:UN7GK,cw,14025000,
-	// -16776961,test;"). ExpertSDR silently drops a spot whose colour field it
-	// can't parse as a number, which is why spots never showed on the panorama
-	// while tuning (a separate command) still worked.
+	// The colour is a DECIMAL ARGB integer, and an UNSIGNED one.
+	//
+	// Expert Electronics' own protocol document gives the whole command:
+	//
+	//	SPOT:RN6LHF,CW,7100000,16711680,ANY_TEXT;
+	//
+	// 16711680 is 0x00FF0000 — positive, alpha zero. This backend was sending
+	// the same number as a SIGNED 32-bit value, taken from a third-party
+	// example: with the alpha byte set to FF for opacity, 0xFFFFA500 becomes
+	// -22336, and a spot whose colour field ExpertSDR cannot read is dropped in
+	// silence. Reported on ExpertSDR3 1.3 (which speaks TCI 2.x, so the version
+	// was never the problem): everything else worked and the panorama stayed
+	// empty.
 	hex := strings.TrimPrefix(strings.TrimPrefix(strings.TrimSpace(s.Color), "#"), "0x")
 	if hex == "" {
 		hex = "FFFFA500" // opaque orange default
@@ -266,7 +279,15 @@ func (t *TCI) SendSpot(s SpotInfo) error {
 	}
 	// Commas/semicolons would break TCI's comma-separated argument parsing.
 	text := strings.NewReplacer(",", " ", ";", " ").Replace(s.Comment)
-	return t.send(fmt.Sprintf("spot:%s,%s,%d,%d,%s;", call, mode, s.FreqHz, int32(argb), text))
+	cmd := fmt.Sprintf("spot:%s,%s,%d,%d,%s;", call, mode, s.FreqHz, argb, text)
+	// The first few, verbatim. A spot that the radio ignores leaves no trace at
+	// all — no reply, no error — so the only evidence that OpsLog sent one, and
+	// in what shape, is this line.
+	if n := t.spotsSent; n < 3 {
+		t.spotsSent = n + 1
+		debugLog.Printf("TCI: sending spot #%d: %s", n+1, strings.TrimSuffix(cmd, ";"))
+	}
+	return t.send(cmd)
 }
 
 // Disconnect closes the WebSocket; the reader goroutine then exits.