Function check_math_body 

pub fn check_math_body(
    source: &str,
    profile: &RenderProfile,
) -> Vec<RenderIssue>

Check source (one math body, no enclosing delimiters) against profile.

The check is single-pass over the lexer event stream from mdwright-latex: each command and environment is classified into “ok” / “needs package” / “unsupported” by consulting the profile’s renderer table, the mdwright-latex registry fallback, and the profile’s package mask. Issues come back in source order; the result is empty when the body is fully compatible.