fix: guard ProgressBarState.String against out-of-range values

tea.go

@@ -319,13 +319,17 @@ const (
 
 // String return a human-readable value for the given [ProgressBarState].
 func (s ProgressBarState) String() string {
-	return [...]string{
+	names := [...]string{
 		"None",
 		"Default",
 		"Error",
 		"Indeterminate",
 		"Warning",
-	}[s]
+	}
+	if s < 0 || int(s) >= len(names) {
+		return fmt.Sprintf("ProgressBarState(%d)", int(s))
+	}
+	return names[s]
 }
 
 // ProgressBar represents the terminal progress bar.

tea_test.go

@@ -669,3 +669,22 @@ func BenchmarkTeaRun(b *testing.B) {
 		_ = r.CloseWithError(io.EOF)
 	}
 }
+
+func TestProgressBarStateString(t *testing.T) {
+	for _, tc := range []struct {
+		state ProgressBarState
+		want  string
+	}{
+		{ProgressBarNone, "None"},
+		{ProgressBarDefault, "Default"},
+		{ProgressBarError, "Error"},
+		{ProgressBarIndeterminate, "Indeterminate"},
+		{ProgressBarWarning, "Warning"},
+		{ProgressBarState(5), "ProgressBarState(5)"},
+		{ProgressBarState(-1), "ProgressBarState(-1)"},
+	} {
+		if got := tc.state.String(); got != tc.want {
+			t.Errorf("ProgressBarState(%d).String() = %q, want %q", int(tc.state), got, tc.want)
+		}
+	}
+}