Omnigraph: Resolver.underlying (unwrap proxy / composite resolvers)

[shrugs]

Problem

Portal's /$name/resolver view needs the "underlying" resolver address when the configured resolver is a proxy / composite resolver. Today this is done with two RPC hops: supportsInterface(CompositeExtendedResolver) to detect the case, then ensjs getUnderlyingAddress to unwrap. As portal migrates off RPC, Omnigraph should expose this directly.

Proposal

Expose on Resolver:

type Resolver {
  # existing fields...
  underlying: Resolver             # null when not a proxy / composite
  isComposite: Boolean!            # optional ERC165 boolean, joining other is* booleans
}

• underlying points at the Resolver entity the proxy delegates to (same node type, so all existing resolver fields are available on it).
• isComposite may not be necessary, ui can just check Resolver.underlying for full

Consumers

• apps/portal/ /$name/resolver
• apps/portal/ features/resolver/hooks/useUnderlyingResolver.ts (current RPC path)