## Problem
`TestXiaomiNewModelWithCustomDefaultTransport` panics on Go 1.25:
```
panic: interface conversion: http.RoundTripper is models.roundTripperFunc, not *http.Transport
```
In Go 1.25, `http.DefaultTransport` is no longer `*http.Transport`, so
the unchecked type assertion in `NewXiaomiModel` panics when the test
replaces it with a `roundTripperFunc`.
## Fix
Use a safe type assertion with fallback to a new `http.Transport`,
matching the pattern already used in `modelscope.go`.
## Verification
```bash
go test -run TestXiaomiNewModelWithCustomDefaultTransport ./internal/entity/models/...
# PASS
```
Internal contributors only.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
---------
Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>
### What problem does this PR solve?
**Verified from CLI**
```
RAGFlow(user)> chat with 'mimo-v2.5@test@xiaomi' message 'who r u'
Answer: Hello! I'm MiMo-v2.5, a large language model developed by Xiaomi's LLM Core Team. You can think of me as a friendly AI assistant ready to help you answer questions, have conversations, or work on creative tasks. My context window can handle up to 1 million tokens, so we can dive into pretty long discussions or documents if you'd like. What can I help you with today?
Time: 3.831830
RAGFlow(user)> stream chat with 'mimo-v2.5@test@xiaomi' message 'who r u'
Answer: there! I'm MiMo-v2.5, an AI assistant created by the Xiaomi LLM Core Team. I'm here to chat, help out, answer questions, or just have a friendly conversation. Think of me as a helpful buddy with a pretty big memory (1 million tokens worth!). What can I do for you today?😊
Time: 2.421630
RAGFlow(user)> think chat with 'mimo-v2.5@test@xiaomi' message 'who r u'
Thinking: The user is asking a simple question about who I am. According to my system prompt, I should:
- Identify myself as **MiMo-v2.5**
- State that I was developed by the **Xiaomi LLM Core Team**
- Answer in first person and be warm and conversational
Answer: Hey there! 👋
I'm **MiMo**, an AI assistant created by the **Xiaomi LLM Core Team**. Think of me as a friendly chat buddy who's here to help you with all sorts of questions and tasks!
I love having conversations, answering questions, brainstorming ideas, and helping people figure things out. Whether you want to chat, need help with something specific, or just want to explore ideas together — I'm here for it! 😊
What can I help you with today?
Time: 6.651589
RAGFlow(user)> tts with 'mimo-v2.5-tts@test@xiaomi' text 'hello? show yourself' play format 'wav' param '{"voice": "Chloe"}'
SUCCESS
RAGFlow(user)> asr with 'mimo-v2.5-asr@test@xiaomi' audio './internal/test.wav' param '{"language": "zh"}'
+------------------------------------------------------------------------------------------------------------------------+
| text |
+------------------------------------------------------------------------------------------------------------------------+
| 1 The examination and testimony of the experts enabled the commission to conclude that five shots may have been fired. |
+------------------------------------------------------------------------------------------------------------------------+
```
### Type of change
- [x] New Feature (non-breaking change which adds functionality)
- [x] Refactoring
