feat: enable prepared statement plan caching via adhoc: false in relation queries

Read adhoc from N1ql.config in build_query_options so all Relation-based
queries (.where, .all, .first, .last, .ids, update_all, delete_all, etc.)
also benefit from server-side plan caching without any caller changes.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: pimpin

lib/couchbase-orm/relation.rb

@@ -238,7 +238,10 @@ def build_update_with_params(params, **cond)
             end
 
             def build_query_options(positional_parameters: [])
-                opts = { scan_consistency: CouchbaseOrm::N1ql.config[:scan_consistency] }
+                opts = {
+                    scan_consistency: CouchbaseOrm::N1ql.config[:scan_consistency],
+                    adhoc: CouchbaseOrm::N1ql.config[:adhoc]
+                }
                 opts[:positional_parameters] = positional_parameters unless positional_parameters.empty?
                 Couchbase::Options::Query.new(**opts)
             end

spec/relation_spec.rb

@@ -501,5 +501,10 @@ def self.active
             end
         end
     end
+
+    it "should use adhoc: false by default for prepared statement plan caching" do
+        expect(Couchbase::Options::Query).to receive(:new).with(hash_including(adhoc: false)).and_call_original
+        RelationModel.where(active: true).ids
+    end
 end