options.theme Not working and unclear what it should do

[mitchuman]

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Describe the bug

The theme option does not seem to work? Should it update the theme inside the Sanity Studio or does it set the default theme name in the JSON output?

To Reproduce

defineField({
	type: 'code',
	options: {
		theme: 'dark-plus', // 👈
		withFilename: true,
	},
})

Expected behavior

Also not mentioned in documentation what the option specifically does.

Which versions of Sanity are you using?

@sanity/cli (global)          3.38.0 (latest: 3.45.0)
@sanity/code-input             4.1.4 (up to date)
@sanity/dashboard              3.1.6 (up to date)
@sanity/eslint-config-studio   4.0.0 (up to date)
@sanity/vision                3.45.0 (up to date)
sanity                        3.45.0 (up to date)

What operating system are you using?
macOS Sonoma 14.5

Which versions of Node.js / npm are you running?

9.5.0
v18.15.0