Entity energy and fluids

entity.capability(host, &ENTITY_ENERGY, side) and entity.capability(host, &ENTITY_FLUIDS, side) reach a mod's entity energy and fluid handlers (NeoForge 26.3's Capabilities.Energy.ENTITY and Capabilities.Fluid.ENTITY), where side is the Option<Direction> of the entity the lookup reaches it from, None for no particular side. Vanilla answers neither; register a provider with r.entity_capability(&ENTITY_ENERGY, "mymod:robot", |host, robot, side| …), which is given that side and may answer differently for each. An entity capability's context is its key's second type: () for ENTITY_ITEMS, Option<Direction> for these two and for ENTITY_AUTOMATION. The existing move_energy and move_resources transfer between these and block or item handlers inside a transaction.