Portal no longer crashes on a self-referencing data graph

Two places in the data layer computed an object's hash code by walking everything it contained. When the data pointed back at itself — which happens routinely once a synchronization stream or an entity store is involved — that walk never finished and the portal process died on the spot, taking every page open on that instance with it.

Streams and their configuration now compare and hash by identity, which is what they always meant: two live streams are two different streams, never two copies of the same value. Stores and collections hash from their keys and sizes instead of from the arbitrary objects they carry, so the cost no longer grows with the size of your workspace either.

A related crash is fixed at the same time: an empty store used to throw when something asked for its hash code.