Qwen2.5-VL text generation crashes: Qwen25_7BVLI_Config is missing stop_tokens

### Description
Using a Qwen2.5-VL text encoder for text generation (e.g. the built-in `TextGenerate` node, or calling `clip.generate()` directly) crashes with:

AttributeError: 'Qwen25_7BVLI_Config' object has no attribute 'stop_tokens'

### Steps to reproduce
1. Load a Qwen2.5-VL text encoder (e.g. `Qwen2.5-VL-7B-Instruct` GGUF / safetensors).
2. Use the `TextGenerate` node, or call `clip.generate(prompt)` in code.
3. Generation starts and then raises `AttributeError` on `self.model.config.stop_tokens` inside `transformer.generate()` (comfy/text_encoders/llama.py).

### Root cause
`transformer.generate()` falls back to reading `self.model.config.stop_tokens` to know when to stop on EOS. Every other Qwen config in `comfy/text_encoders/llama.py` defines `stop_tokens = [151643, 151645]`, but `Qwen25_7BVLI_Config` omits it, so the attribute lookup fails.

### Expected
Generation completes and returns token ids (terminating on `<|im_end|>` / `<|endoftext|>`), instead of raising.

### Fix
Add `stop_tokens = [151643, 151645]` to `Qwen25_7BVLI_Config`. PR to follow.

Open comfy/text_encoders/llama.py and inspect Qwen25_7BVLI_Config alongside the other Qwen configurations. Run the TextGenerate or clip.generate() reproduction with a Qwen2.5-VL encoder, then verify generation returns token IDs and terminates on the expected end tokens without the AttributeError.

Written by the indexing model from the issue text.