Module chain 

A chain scope: the subgraph reachable from one root along a named rel-type set in one direction — the reduced set the export formats and the topology projection render when a caller asks for a chain instead of a whole mem.

One resolver, one walker. The scope is resolved here once, through reachable_via — the same primitive memstead_search’s expand_via uses, so direction means the same thing on both surfaces: applied at EVERY hop, a pure transitive closure. The renderers then filter their existing per-entity passes by the resolved set; nothing is rendered twice and no second walker exists.

Structs

ChainScope

What a caller asks for: a root entity, the rel-types to follow, the direction to follow them in, and how many hops.

ChainSet

A resolved chain: the root plus everything reached, in any mem. The renderers filter to their mem; cross-mem members stay in the set so an edge into one renders as a reached (marked) target, not as an unresolved link.