DisplayRule

A purely visual rule over displayed input values. Rules never affect what is exported — that guarantee is structural, since the module evaluating them is never imported on the export path.

Key	Type	Required	Notes
name	string	yes	Identifies the rule; shown in diagnostics and used as a stable render key. min length 1, matches ^[A-Za-z0-9_-][A-Za-z0-9_ -]*[A-Za-z0-9_-]$|^[A-Za-z0-9_-]$
when	Condition	yes	The condition that fires this rule.
appliesTo	array of string	no	Fields to style when the rule fires. Defaults to the field the condition tests, which is what you want for a single-field rule and never what you want when comparing two. at least 1 item
style	Style	yes	How the matched fields are styled.