Feature: brand-mode to choose light or dark brand in Typst

[gordonwoodhull]

As promised, this turned out to be quite simple once everything else was in place.

Filing as draft because

• this needs a better name than choose-brand
• some lingering cases in typst_css.lua where it needs access to choose-brand instead of hard-coded brandMode = 'light'
• needs tests

Cases like

quarto-cli/tests/docs/smoke-all/typst/brand-yaml/color/typst-css-named-brand-color.qmd

Lines 26 to 28 in 5df4e19

	:::{style="background-color: var(--brand-dark-grey); color: var(--brand-blue)"}
	This div is blue on dark grey.
	:::

[cscheid]

LGTM aside from the schema name.

Renamed to brand-mode

[gordonwoodhull]

Note: this doesn't consider author preference, i.e. if dark is put before light in brand or theme, brand-mode will still default to light.

Since we are moving away from author preference online #12426, this seems less urgent. But it could in theory be initialized from TS in the Quarto front-end. Order of YAML objects is unavailable in Lua metadata! 😮