[iluvatar] runtime path imports pytest: triton/spec/iluvatar/triton/testing.py::nvsmi reaches triton._internal_testing

### Summary

`triton/spec/iluvatar/triton/testing.py::nvsmi` imports `triton._internal_testing` for `is_corex`, and that module does `import pytest` at module level. `nvsmi` is reachable from a **production** call path (no test involvement), so on an iluvatar box without pytest, serving a model dies with `ModuleNotFoundError: No module named 'pytest'`.

### Version

`flagtree==0.6.1+iluvatar3.6` (the wheel installed into `flagos-runtime-iluvatar-corex4.5.0:2.1.2`, python 3.12).

### Call path

```
flag_gems _iluvatar mm/addmm tuned configs carry
prune_configs_by={"perf_model": estimate_matmul_time, ...}
-> triton/runtime/autotuner.py::prune_configs
-> triton/ops/matmul_perf_model.py::estimate_matmul_time
-> triton/ops/matmul_perf_model.py::get_tflops
-> triton/ops/matmul_perf_model.py::get_tensorcore_tflops
-> triton/ops/matmul_perf_model.py::get_clock_rate_in_khz
-> triton/spec/iluvatar/triton/testing.py::nvsmi <-- here
-> from triton._internal_testing import is_corex
-> triton/_internal_testing.py:31 import pytest <-- fails
```

Observed while serving Qwen3-4B on sglang 0.5.18 (decode attention autotuning):

```
File "/opt/flagtree/triton/ops/matmul_perf_model.py", line 14, in get_clock_rate_in_khz
return nvsmi(['clocks.max.sm'])[0] * 1e3
File "/opt/flagtree/triton/spec/iluvatar/triton/testing.py", line 8, in nvsmi
from triton._internal_testing import is_corex
File "/opt/flagtree/triton/_internal_testing.py", line 31, in
import pytest
ModuleNotFoundError: No module named 'pytest'
```

### Why it is a packaging defect rather than a caller problem

The equivalent helper in the vendor triton this stack also ships (`triton==3.2.0+corex.4.5.0.20260804`) defines `is_corex()` locally in `triton/testing.py` and imports nothing from `_internal_testing`:

```python
def is_corex():
import torch
return hasattr(torch, "corex") and torch.corex == True
```

So the spec overlay reaches into a test-support module for a one-line predicate, and by doing so drags a test framework into the runtime dependency set of every flagtree+iluvatar install.

### Suggested fix

Define `is_corex()` locally in `triton/spec/iluvatar/triton/testing.py` (as vendor triton does), or move `is_corex` out of `_internal_testing.py` into a module that does not import pytest.

### Workaround in use

Installing `pytest` into the image. FlagOS carries it until this is fixed — tracked as an explicit app dependency with a pointer back to this issue.

Start with triton/spec/iluvatar/triton/testing.py::nvsmi and compare its is_corex dependency with the vendor triton testing.py implementation described in the issue. Check triton/_internal_testing.py to confirm the pytest import path, then verify that the production nvsmi call path can load without pytest; done means the runtime no longer requires pytest for this path.

Written by the indexing model from the issue text.