### What problem does this PR solve?
New default prompt:
```
You are an intelligent assistant. Your primary function is to answer questions based strictly on the provided knowledge base.
**Essential Rules:**
- Your answer must be derived **solely** from this knowledge base: `{knowledge}`.
- **When information is available**: Summarize the content to give a detailed answer.
- **When information is unavailable**: Your response must contain this exact sentence: "The answer you are looking for is not found in the knowledge base!"
- **Always consider** the entire conversation history.
```
Also fix some grammar errors.
### Type of change
- [x] Refactoring
Signed-off-by: Jin Hai <haijin.chn@gmail.com>
### What problem does this PR solve?
1. Fix error of book chunking.
2. Fix format issues.
### Type of change
- [x] Bug Fix (non-breaking change which fixes an issue)
- [x] Refactoring
---------
Signed-off-by: Jin Hai <haijin.chn@gmail.com>
### What problem does this PR solve?
#9082#6365
<u> **WARNING: it's not compatible with the older version of `Agent`
module, which means that `Agent` from older versions can not work
anymore.**</u>
### Type of change
- [x] New Feature (non-breaking change which adds functionality)
