UnderlineStyle
UnderlineStyle =
"single"|"double"|"curly"|"dotted"|"dashed"
Defined in: src/render/style.ts:7
Underline rendering style. single is the classic flat line; the rest map to
the colon sub-parameter forms standardised by Kitty and supported by Ghostty,
iTerm2, WezTerm, and our web/canvas backend. curly (undercurl) is the
conventional cue for spelling/diagnostic squiggles.