can_show only asked the installed-font lookups for those two languages, and
both lookups hard-code None on wasm32, where there are no system fonts. The
Korean gate already falls back to a craft-fonts face (korean_font), but the
web build embeds a Jpan CJK face and an Arabic face precisely as the web's
only fonts, so a Chinese or Arabic interface could never be selected on it,
however complete the catalog; the embedded Arabic face was also never added
to the UI font families (the embedded filter only kept Jpan/Han faces).
Give both gates the embedded-face path the Korean one has:
- can_show("zh"/"ar") answers true when this build embeds a Regular face of
Hans/Hant or Arab, in addition to an installed font.
- install_fonts picks embedded faces via embedded_ui_faces: every CJK face
still loads in every language for CJK drawing names (#513), the face of a
zh interface leads (a Japanese face lacks the simplified-only 图 园 测),
and an Arabic interface appends its Arabic face.
Nothing changes for a build without CRAFT_FONTS_DIR (CRAFT_FONTS empty):
Chinese still rides on an installed CJK font and Arabic on an installed one.
