Can't compute multiple embeddings in a single call

# Prerequisites

Please answer the following questions for yourself before submitting an issue.

- [x] I am running the latest code. Development is very rapid so there are no tagged versions as of now.
- [x] I carefully followed the [README.md](https://github.com/abetlen/llama-cpp-python/blob/main/README.md).
- [x] I [searched using keywords relevant to my issue](https://docs.github.com/en/issues/tracking-your-work-with-issues/filtering-and-searching-issues-and-pull-requests) to make sure that I am creating a new issue that is not already open (or closed).
- [x] I reviewed the [Discussions](https://github.com/abetlen/llama-cpp-python/discussions), and have a new bug or useful enhancement to share.

# Expected Behavior

Running this code:

```python
model = llama_cpp.Llama ("mxbai-embed-xsmall-v1-q8_0.gguf", embedding = True)
embeddings = model.embed (["Hello", "World"])
```

used to work in v0.3.14

# Current Behavior

The code raises an exception `RuntimeError: llama_decode returned -1`. The following messages are printed to the console:

```
init: invalid seq_id[3][0] = 1 >= 1
encode: failed to initialize batch
```

# Environment and Context

llama-cpp-python was compiled in CUDA mode

# Failure Information (for bugs)

Please help provide information about the failure if this is a bug. If it is not a bug, please remove the rest of this template.

# Steps to Reproduce

```python
Python 3.11.2 (main, Apr 28 2025, 14:11:48) [GCC 12.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import llama_cpp
>>> model = llama_cpp.Llama ("../models/mxbai-embed-xsmall-v1-q8_0.gguf", embedding = True)
...
>>> embeddings = model.embed (["Hello", "World"])
decode: cannot decode batches with this context (calling encode() instead)
init: invalid seq_id[3][0] = 1 >= 1
encode: failed to initialize batch
llama_decode: failed to decode, ret = -1
Traceback (most recent call last):
File "", line 1, in
File ".../site-packages/llama_cpp/llama.py", line 1108, in embed
decode_batch(s_batch)
File ".../site-packages/llama_cpp/llama.py", line 1045, in decode_batch
self._ctx.decode(self._batch)
File ".../site-packages/llama_cpp/_internals.py", line 327, in decode
raise RuntimeError(f"llama_decode returned {return_code}")
RuntimeError: llama_decode returned -1
```

Lỗi xảy ra trong llama_cpp/llama.py, khoảng dòng 1108 trong phương thức embed và dòng 1045 trong decode_batch. Trước tiên, hãy kiểm tra việc khởi tạo batch và xử lý ID chuỗi trong các binding C++ (_internals.py). Xem xét những thay đổi trong logic embedding giữa v0.3.14 và phiên bản hiện tại. Chạy script tái hiện được cung cấp để xem lỗi chính xác, sau đó kiểm tra việc giải mã batch của thư viện llama.cpp cho nhiều chuỗi.

Do mô hình lập chỉ mục viết ra từ nội dung của issue.