Spark DSL transformer that wires up resolve_argument declarations.

For every resolve_argument :name, from_path: [...] declaration:

1. Validates the path at compile time (intermediates are belongs_to, leaf is an attribute).
2. Validates that at least one scope references ^arg(:name) in its resolved filter (rejecting dead declarations).
3. For every targeted write action (:create, :update, :destroy, or the explicit :for_actions list), injects:
   • an argument :name, <type>, allow_nil?: true with the type inferred from the leaf attribute (if the action does not already declare it)
   • a change {AshGrant.Changes.ResolveArgument, [name:, path:, scopes_needing:]} with scopes_needing computed at compile time