keepDirectInterfaces

Direct-interface projection: keep only edges with at least one endpoint INSIDE the analysed element, and drop outside nodes left unconnected to it. "Inside" = the element node, or any construct whose own name — or an ancestor's, walking parentConstructId — lies within elementNamespace (the element's own code, vs external stdlib / harness / other-component code that taint merely flows through). Inside nodes are always kept; outside nodes survive only when an edge ties them to an inside node; compound ancestors of kept nodes are kept so their boxes survive.

No-op unless elementNamespace is known — an element id alone makes only the element node "inside" (never an edge endpoint), which would hide the entire graph. So membership needs the namespace signal.