fix(product): Correctly handle nested memory structure in chat methods

[muzzlol]

Description

Summary: This PR fixes an AttributeError that occurred in both chat() and chat_with_references() when processing memory references for streaming responses. The root cause was an incorrect assumption about the data structure returned from the search method.

Fix: #(no existing issue - bug found during development)

Docs Issue/PR: (not applicable)

Reviewer: @(leave blank)

Root Cause

The super().search() method returns a list of dictionaries, where each dictionary is structured as {"cube_id": "...", "memories": [TextualMemoryItem, ...]}.

The code was incorrectly trying to access attributes like .id and .model_dump() on the outer dictionary instead of on the TextualMemoryItem objects contained within the "memories" key.

Solution

A nested loop has been added to correctly iterate through the TextualMemoryItem objects. This ensures we are operating on the actual Pydantic models and can access their attributes without error.

Checklist:

• I have performed a self-review of my own code | 我已自行检查了自己的代码
• I have commented my code in hard-to-understand areas | 我已在难以理解的地方对代码进行了注释
• I have added tests that prove my fix is effective or that my feature works | 我已添加测试以证明我的修复有效或功能正常
• I have created related documentation issue/PR in MemOS-Docs (if applicable) | 我已在 MemOS-Docs 中创建了相关的文档 issue/PR（如果适用）
• I have linked the issue to this PR (if applicable) | 我已将 issue 链接到此 PR（如果适用）
• I have mentioned the person who will review this PR | 我已提及将审查此 PR 的人

[fridayL]

Sorry for the late code review.
first please change pr branch to dev
and for the code I want to clarify that at lines 757-762:

memories_list = []
memories_result = super().search(
    query, user_id, install_cube_ids=[cube_id] if cube_id else None, top_k=10
)["text_mem"]
if memories_result:
    memories_list = memories_result[0]["memories"]

I have already handled this part maybe is not very good style.
If you want to change the structure later, you'll also need to update this code accordingly.

[CaralHsi]

Please resolve the conflicts. Thanks for your contribution:)