Fix [Spark unit test CI]: defer torch._dynamo.disable to avoid import-time crash in CI (#3290)

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## 📌 Description

- #3271 (feat(moe): add SM120 W4A16 b12x kernels) added a
@torch._dynamo.disable decorator to current_cuda_stream() in
cute_dsl/utils.py. This eagerly imports torch._dynamo at module load
time, which triggers getpass.getuser() during cache-dir initialization.
This crashes in CI containers running as unmapped UIDs (e.g. Spark
runners with -u $(id -u):$(id -g) mapping to UID 996, which has no
/etc/passwd entry).
- Replaces the eager decorator with a self-replacing lazy wrapper that
defers torch._dynamo.disable to the first call of current_cuda_stream(),
with zero overhead on subsequent calls.

## 🔍 Related Issues

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## 🧪 Tests

- [x] Tests have been added or updated as needed.
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## Summary by CodeRabbit

* **Performance**
* Improved module import performance by deferring CUDA stream
initialization until first use, reducing startup overhead.

[![Review Change
Stack](https://storage.googleapis.com/coderabbit_public_assets/review-stack-in-coderabbit-ui.svg)](https://app.coderabbit.ai/change-stack/flashinfer-ai/flashinfer/pull/3290)

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Co-authored-by: Cursor <cursoragent@cursor.com>