Function get_current_prefix 

pub fn get_current_prefix(
    query: Query<'_, '_, (Entity, &Element, &Prefixes, &PositionComponent, &RopeC), Changed<PositionComponent>>,
    commands: Commands<'_, '_>,
)

Detect whether the cursor sits on a prefix declaration / JSON-LD @context term and, if so, insert a PrefixComponent and drop the (necessarily wrong) TripleComponent. Shared by the Hover and GotoDefinition schedules.