Node

Represents the three types of nodes in our call graph:

• LocalDef: a method definition in local code, with a code hash
• Call: a method call site, connecting to its resolved local destinations
• ExternalClsCall(dest, narrow): a shared proxy node for external callback edges. dest determines which callback methods are possible (by walking dest's ancestors in externalClassLocalDests). narrow determines which local subtypes receive those callbacks (subtypes of narrow). When a precise bytecode type (receiver or arg) is a subtype of dest, it serves as narrow for more precise fan-out; otherwise dest == narrow (no narrowing).