(() => {
  const allowedThemes = new Set(["system", "light", "dark"]);
  let theme = "system";

  try {
    const savedTheme = window.localStorage.getItem("roster-theme");
    if (allowedThemes.has(savedTheme)) {
      theme = savedTheme;
    }
  } catch {
    // Storage can be unavailable in hardened or private browsing contexts.
  }

  document.documentElement.dataset.theme = theme;
})();