fix(elecraft): read the SWR as three digits, not four

Elecraft's release note settles it: SW; returns the most recent reading in
transmit or TUNE as three digits in tenths of a ratio — SW023 is 2.3:1,
and SW999 is the 99.9:1 it reports instead of infinity.

This asked for four, so every answer failed to parse and the bar stayed
empty for the whole transmission. A tester saw exactly that: no SWR at
all, which reads as an unsupported radio rather than an off-by-one.

SW also comes out of the probe list. It is known now, and asking again
mid-transmission costs a round trip on the link the carrier depends on.

internal/cat/kenwood_panel.go

@@ -15,6 +15,10 @@ package cat
 //     good match on a bad antenna. So the raw answers are LOGGED, for a real
 //     radio to settle, and until then the panel says the scaling is provisional.
 //
+// SWR is settled: SW; answers three digits in tenths of a ratio ("SW023;" =
+// 2.3:1), from Elecraft's release note. The power meter is still read from the
+// bargraph and still provisional.
+//
 // The same discipline as the Yaesu meters, which were guessed wrong twice and
 // only settled when an FTDX10 keyed a carrier at two known power levels.
 
@@ -309,7 +313,9 @@ func kenwoodAGCValue(name string) int {
 // answered and what it said, next to the power SETTING: the meter that tracks a
 // known carrier at two different power levels is the power meter, and no amount
 // of reading the reference settles that as well as one transmission does.
-var kenwoodMeterProbes = []string{"SM;", "SMH;", "BG;", "SW;", "PO;", "TQ;"}
+// SW is no longer among them: it is known, read above, and asking again during
+// a transmission costs a round trip on the one link the carrier depends on.
+var kenwoodMeterProbes = []string{"SM;", "SMH;", "BG;", "PO;", "TQ;"}
 
 // readTXMeters reads the transmit meters.
 func (k *Kenwood) readTXMeters() {
@@ -321,10 +327,12 @@ func (k *Kenwood) readTXMeters() {
 	if v, ok := k.askNum("BG;", "BG", 2); ok {
 		k.panel.PowerMeter = k.powerPeak.update(kenwoodBargraphPercent(v), now)
 	}
-	if v, ok := k.askNum("SW;", "SW", 4); ok {
+	// SW; — SETTLED, from Elecraft's own release note: three digits, tenths of a
+	// ratio. "SW023;" is 2.3:1, and "SW999;" is the 99.9:1 it reports instead of
+	// infinity. This was reading FOUR digits, so every answer failed to parse
+	// and the bar stayed empty — which is why a tester saw no SWR at all.
+	if v, ok := k.askNum("SW;", "SW", 3); ok {
 		k.panel.SWRRaw = v
-		// Tenths of a ratio, provisionally: 15 → 1.5. Reported as raw as well,
-		// so the log can correct this without anyone having to trust the bar.
 		if v > 0 {
 			k.panel.SWR = float64(k.swrPeak.update(v, now)) / 10
 		}