feat(tci): the transmit meters, and no temperature invented

TX_POWER and TX_SWR are read-only commands the radio answers when asked,
so they are asked for on each poll of a KEYED radio and not at all
otherwise: a receiving station pays nothing for meters nobody is watching.
Both appear next to the S-meter only while transmitting, because showing
them the rest of the time would show the last thing that happened as if it
were now.

An SWR of 0 draws as '—' rather than as 1.0. A perfect match on an antenna
nobody has measured is the one reading an operator should never be handed.

There is no temperature. The protocol's command list has TX_POWER and
TX_SWR and nothing thermal at all — so rather than leave the question
hanging, it is written down where the next person will look for it. A
temperature invented from something else, on a transmitter, is exactly the
kind of number somebody would trust.

internal/cat/flex.go

@@ -59,7 +59,7 @@ type Flex struct {
 	meterRawLogged bool         // log the first raw meter-definition status once
 	txRawLogged    bool         // log the first raw transmit status once (field-name audit)
 
-	spotsEnabled    bool           // push cluster spots + manage the panadapter overlay
+	spotsEnabled bool // push cluster spots + manage the panadapter overlay
 	// foreignSpotSeen counts what probeForeignSpot has already reported, so a
 	// skimmer posting all evening cannot turn the log into its own transcript.
 	foreignSpotSeen int