【Hackathon 9th No.38】Unit test for winx_unzip

[cloudforge1]

Add unit tests for the winx_unzip (wint2 unzip) op used in low-bit quantization.

Source: custom_ops/gpu_ops/moe/winx_unzip.cu
Registration: custom_ops/gpu_ops/cpp_extensions.cc
Test file: tests/operators/test_winx_unzip.py

Should test unpacking of compressed integer weights back to full representation. Verify correctness across different tensor shapes.

Branch: task/038-winx-unzip-test