Function check_block_light_chunk_edges 

pub fn check_block_light_chunk_edges(
    workset: &LightWorkset,
) -> Result<BlockLightUpdateResult, BlockLightPropagationContextError>

Validates already-loaded block-light chunk edges without resetting sections.

This matches ScalableLux checkBlockEdges: the force-load pass has already synchronized empty-section state, so this pass only checks horizontal consistency against loaded neighbors and publishes its own dirty sections.