Function validate_detail 

pub fn validate_detail(
    spec: &Value,
    options: &ValidateDetailOptions<'_>,
) -> Result<(), ComposeLoadError>

Validate a detail-spec’s STRUCTURE: compose then forbidden-scan (§6).

Returns Ok(()) when the composed detail tree carries no forbidden meta key. Returns Err(ComposeLoadError) for an unresolved composition ($ref/$patch) or a forbidden meta key at any depth (FORBIDDEN_META_KEY). Both are LOAD failures, never a valid:false result.