Function add_missing_prefix_code_action 

pub fn add_missing_prefix_code_action(
    query: Query<'_, '_, (&Element, &Prefixes, &Source, &RopeC, &Label, &DynLang, &mut CodeActionRequest), With<Open>>,
    lovs: Query<'_, '_, &LocalPrefix>,
    prefix_cc: Query<'_, '_, &PrefixEntry>,
    config: Res<'_, ServerConfig>,
)

ECS system: runs prefix_diagnostic_helper for every open document to populate CodeActionRequest with “Add prefix declaration” quickfixes.

Skips languages that opt out via LangHelper::supports_prefix_diagnostics.