chore(tci): cap the diagnostic logging per message type

The transmit meters are asked for four times a second while keyed, so
logging every arrival would fill an evening's log — and a diagnostic that
fills a log is one that gets switched off instead of read. Twenty of each
is enough to tell an answer from a silence, which is all it is for.

internal/cat/tci_panel.go

@@ -88,6 +88,8 @@ type TCIPanelState struct {
 // arrives alongside.
 type tciPanel struct {
 	st TCIPanelState
+	// logged counts what has been written per message type — see handlePanel.
+	logged map[string]int
 }
 
 // handlePanel takes the messages the console cares about.
@@ -112,12 +114,21 @@ func (t *TCI) handlePanel(name string, get func(int) string, args string) bool {
 	// this is our reading or its doing, and no amount of reasoning will.
 	switch name {
 	case "mute", "sql_enable", "sql_level", "tx_power", "tx_swr", "tune":
-		// Logged on arrival so an ANSWER can be told from a silence. The
+		// Logged on arrival so an ANSWER can be told from a SILENCE: the log
-		// transmit meters are asked for four times a second while keyed and the
+		// showed the transmit meters being asked for and nothing coming back,
-		// log showed only the asking, which proves nothing on its own: a reply
+		// which on its own proves nothing — a reply that arrived and failed to
-		// that arrived and failed to parse looks exactly like one that never
+		// parse leaves exactly the same trace as one that never came.
-		// came.
+		//
-		debugLog.Printf("TCI: %s:%s", name, args)
+		// Capped per message type. The meters are asked for four times a second
+		// while transmitting, and a diagnostic that fills an evening's log is
+		// one that gets switched off instead of read.
+		if t.panel.logged == nil {
+			t.panel.logged = map[string]int{}
+		}
+		if n := t.panel.logged[name]; n < 20 {
+			t.panel.logged[name] = n + 1
+			debugLog.Printf("TCI: %s:%s", name, args)
+		}
 	}
 	switch name {
 	case "protocol":