Chat memory advisor causes message ordering problem with default system message prompt

Bug description

Using MessageChatMemoryAdvisor with a default system prompt causes "conversation roles must alternate user/assistant/user/assistant" error. This appears to be the same issue as reported in #2216 which was marked as fixed in 1.0.0-M8 but can be reproduced in 1.0.1.

Environment

• Spring AI version: 1.0.1
• Spring Boot version: 3.5.4
• Java version: 21.0.2
• AI Provider: OpenAI (Docker Model Runner with ai/mistral:latest model for testing)
• Dependencies: spring-ai-starter-model-chat-memory, spring-ai-starter-model-openai

Steps to reproduce

1. Create a ChatClient with defaultSystem() prompt and MessageChatMemoryAdvisor configured
2. Make a chat call with a conversation id
3. Attempt a second chat call with the same conversation id
4. The second call fails with error "After the optional system message, conversation roles must alternate user/assistant/user/assistant..."

The error occurs during the second chatClient.prompt().call().content() call. Upon debugging the MessageChatMemoryAdvisor#before, I can see that messages are collected in the wrong order:

1. UserMessage
2. AssistantMessage
3. SystemMessage
4. UserMessage

Expected behavior

The MessageChatMemoryAdvisor should properly order the system prompt and conversation context to allow for continued dialogue with alternating user/assistant roles without errors.

I would expect messages to be collected in the following order instead which I believe should allow the request to succeed:

1. SystemMessage
2. UserMessage
3. AssistantMessage
4. UserMessage

Minimal Complete Reproducible example

https://github.com/sjohnr/spring-ai-chat-memory-bug