fix(baileys): handle array response in on_whatsapp endpoint

The Baileys `/on-whatsapp` endpoint can return a bare JSON array instead
of a hash with a `data` key. Calling `Array#dig` with a string key
raises `TypeError (no implicit conversion of String into Integer)`,
causing a 500 error. Handle both response shapes.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

app/services/whatsapp/providers/whatsapp_baileys_service.rb

@@ -424,7 +424,9 @@ class Whatsapp::Providers::WhatsappBaileysService < Whatsapp::Providers::BaseSer
 
     raise ProviderUnavailableError unless process_response(response)
 
-    response.parsed_response&.dig('data')&.first || { 'jid' => remote_jid, 'exists' => false }
+    result = response.parsed_response
+    result = result.is_a?(Array) ? result : result&.dig('data')
+    result&.first || { 'jid' => remote_jid, 'exists' => false }
   end
 
   def delete_message(recipient_id, message)

spec/services/whatsapp/providers/whatsapp_baileys_service_spec.rb

@@ -946,6 +946,36 @@ describe Whatsapp::Providers::WhatsappBaileysService do
       end
     end
 
+    context 'when response is an array instead of a hash' do
+      it 'handles the array response correctly' do
+        stub_request(:post, request_path)
+          .with(headers: stub_headers(whatsapp_channel), body: { jids: ["#{phone_number.delete('+')}@s.whatsapp.net"] }.to_json)
+          .to_return(
+            status: 200,
+            headers: { 'Content-Type' => 'application/json' },
+            body: [{ jid: "#{phone_number.delete('+')}@s.whatsapp.net", exists: true }].to_json
+          )
+
+        response = service.on_whatsapp(phone_number)
+
+        expect(response).to eq({ 'jid' => "#{phone_number.delete('+')}@s.whatsapp.net", 'exists' => true })
+      end
+
+      it 'returns default check response when array is empty' do
+        stub_request(:post, request_path)
+          .with(headers: stub_headers(whatsapp_channel), body: { jids: ["#{phone_number.delete('+')}@s.whatsapp.net"] }.to_json)
+          .to_return(
+            status: 200,
+            headers: { 'Content-Type' => 'application/json' },
+            body: [].to_json
+          )
+
+        response = service.on_whatsapp(phone_number)
+
+        expect(response).to eq({ 'jid' => "#{phone_number.delete('+')}@s.whatsapp.net", 'exists' => false })
+      end
+    end
+
     context 'when response is unsuccessful' do
       it 'raises ProviderUnavailableError and logs the error' do
         stub_request(:post, request_path)