Function record_composited_into 

fn record_composited_into<'a, P: RenderPassInterface<'a>>(
    pass: &mut P,
    state: &mut PassState<'a>,
    scenes: &[&'a Scene],
    fallback: Option<ViewportRect>,
)

The composite recorder behind Scene::record_composited, generic over the pass so tests can drive it with a mock.

Three linear passes over the scenes, and a sort over only the pool: the sequenced and trailing draws are emitted in scene order without being compared, so an untagged scene’s batching survives the composite, and a frame whose draws all state no order never sorts at all.