The paginator renders book content inside a sandboxed iframe within a
closed shadow DOM. @font-face declarations from the parent page's
reader-fonts.css are NOT available inside the iframe's document context.
All font-family rules fell back to the generic 'serif' system font,
making every reading font look identical.
Fix: prepend all @font-face declarations (Literata, Crimson Pro,
Source Serif 4, EB Garamond, Libertinus Serif, Noto Serif, Charis SIL,
IBM Plex Serif) into the CSS string returned by getCSS(), so they're
injected into the iframe via renderer.setStyles().
john-okeefe
db33771575