Fix empty block warnings in jetstream_bridge_spec

Replace empty blocks with blocks that explicitly return nil to avoid
Lint/EmptyBlock warnings. Use proper argument names with underscores
for unused block parameters.

All RuboCop checks now pass with zero offenses detected.

Author: attaradev

spec/jetstream_bridge_spec.rb

@@ -88,26 +88,26 @@
     end
 
     it 'returns consumer instance when run: false' do
-      consumer = described_class.subscribe {}
+      consumer = described_class.subscribe { nil }
       expect(consumer).to be_a(JetstreamBridge::Consumer)
     end
 
     it 'returns thread when run: true' do
       allow_any_instance_of(JetstreamBridge::Consumer).to receive(:run!)
 
-      result = described_class.subscribe(run: true) {}
+      result = described_class.subscribe(run: true) { nil }
       expect(result).to be_a(Thread)
       result.kill # Clean up thread
     end
 
     it 'accepts handler as first argument' do
-      handler = -> {}
+      handler = ->(_event, _context) {}
       consumer = described_class.subscribe(handler)
       expect(consumer).to be_a(JetstreamBridge::Consumer)
     end
 
     it 'accepts custom durable_name and batch_size' do
-      consumer = described_class.subscribe(durable_name: 'custom', batch_size: 50) {}
+      consumer = described_class.subscribe(durable_name: 'custom', batch_size: 50) { nil }
       expect(consumer.durable).to eq('custom')
       expect(consumer.batch_size).to eq(50)
     end