The document Code preview and the Host read card each owned an
extension-to-language table that had drifted: the preview table had 13
extensions the read card lacked, and the two returned different language
ids for the same suffix. Both now resolve through the new zero-dependency
@deepseek-ai/dsh-util-code-language, which also adds common Windows,
config, markup, and language extensions. Every added grammar stays in the
lazy set; the boot grammars are unchanged.
Fixes#4822
