Give the words' zone through a seam, so no test writes time.Local under the race detector (novox/hq issue 443)

cmd/mesh-controller/plain_words_test.go

@@ -408,10 +408,12 @@ func TestAnUnansweredMergeCheckSaysWhichCheckAndWhatToDo(t *testing.T) {
 // the finished words it gave before, and the controller words it in its local zone, as every other time in a message.
 // The line is the one mesh-delivery says, as in the report of issue 443, with the checks it now carries.
 func TestAnUnansweredMergeChecksTimeIsSaidInLocalTime(t *testing.T) {
-	was, wasNow := time.Local, wordsNow
-	time.Local = time.FixedZone("CEST", 2*60*60)
+	// The operator's zone given through the seam, never by writing time.Local: other tests' goroutines read it, and
+	// the build seat runs the suite under the race detector.
+	wasZone, wasNow := wordsZone, wordsNow
+	wordsZone = func() *time.Location { return time.FixedZone("CEST", 2*60*60) }
 	wordsNow = func() time.Time { return time.Date(2026, 10, 11, 1, 12, 39, 0, time.UTC) }
-	t.Cleanup(func() { time.Local, wordsNow = was, wasNow })
+	t.Cleanup(func() { wordsZone, wordsNow = wasZone, wasNow })
 
 	var l stalledLine
 	if err := json.Unmarshal([]byte(`{"id":"novox/mesh-controller@c11222026a3b","number":212,"state":"unanswered",`+