Function dispatch_asset_drop 

fn dispatch_asset_drop(
    state: &mut EditorState,
    idx: usize,
    target: Option<EntityId>,
)

Routes an asset dropped onto the hierarchy to the right pending_* action, mirroring the viewport’s drop dispatch. Meshes spawn at the world origin (a tree has no 3D drop point), prefabs instantiate, scenes load, and a texture/material assigns to the target row (or the selection).