Reject every() intervals that overflow int32 milliseconds

Char is rune (int32). Without an upper bound, secs * 1000 could
silently wrap to a non-positive value and panic time.NewTicker.

src/options.go

@@ -1315,8 +1315,11 @@ func parseEveryEvent(arg string) (tui.Event, error) {
 	if secs < 0.01 {
 		secs = 0.01
 	}
-	ms := int32(math.Round(secs * 1000))
-	return tui.Event{Type: tui.Every, Char: rune(ms)}, nil
+	ms := math.Round(secs * 1000)
+	if ms > math.MaxInt32 {
+		return tui.Event{}, errors.New("every() interval is too large")
+	}
+	return tui.Event{Type: tui.Every, Char: rune(int32(ms))}, nil
 }
 
 func parseScheme(str string) (string, []criterion, error) {

src/options_test.go

@@ -323,8 +323,8 @@ func TestParseEveryEvent(t *testing.T) {
 		t.Errorf("every(0.001) should floor to 10ms")
 	}
 
-	// Reject zero and negatives
-	for _, bad := range []string{"every(0)", "every(-1)", "every(abc)", "every()"} {
+	// Reject zero, negatives, and overflow (>= 2^31 ms = ~24.85 days)
+	for _, bad := range []string{"every(0)", "every(-1)", "every(abc)", "every()", "every(2147484)"} {
 		if _, _, err := parseKeyChords(bad, ""); err == nil {
 			t.Errorf("%s should be rejected", bad)
 		}