Restrict the "Choose file…" document picker to font MIME types (font/ttf, font/otf, font/sfnt, font/collection plus legacy application/* font aliases) instead of */*, so only fonts are selectable. CustomFontStore's Font.Builder validation still guards anything a provider mislabels. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>