Both builders construct a ThemeData with the matching brightness +
ColorScheme.dark/.light + the corresponding FabledSwordTheme
extension. buildThemeData() stays as a back-compat alias returning
the dark theme so the existing widget-test suite keeps using it
without churn.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Widgets read tokens via Theme.of(ctx).extension<FabledSwordTheme>().
Material 3 ColorScheme bound to FabledSword tokens. Body text uses
GoogleFonts.interTextTheme() so the fonts work without bundling .ttf
files (offline-from-cold-launch is a separate question once #357 lands).
bvandeusen