Function build_frame_buffer_content 

pub(crate) fn build_frame_buffer_content(
    wave_container: &WaveContainer,
    scope_ref: &ScopeRef,
) -> Option<(Vec<ArrayLevel>, Vec<VariableRef>)>

Analyses the scope hierarchy rooted at scope_ref and returns:

• levels: one ArrayLevel per nesting level, where the last level is for variables
• all_leaf_vars: every variable reachable from the root (for pre-loading)

Returns None when scope_ref is not found in the hierarchy.