Function compute_diff 

pub async fn compute_diff<Q: ForkQueryHost + ?Sized>(
    a: &Q,
    b: &Q,
) -> Result<ForkDiff>

Compute the structural delta between two views.

Both a and b may be primary or forked sessions. The convention is forward: returned ForkDiff.vertices.added is rows present in b but not a; deleted is rows in a but not b.

Identity is content-addressed UID for vertices and (src_uid, dst_uid) for edges, scoped by edge type — so two unrelated forks with overlapping VIDs but distinct content pair correctly.