Pinned Ruff check reports 21 errors in AMD modules

### Description

The repository's pinned pre-commit Ruff version fails on current main commit `8260bc34398c2b8f36dc840fd22f741ca9294584`:

```console
$ ruff 0.9.1 check --config python/pyproject.toml python
Found 21 errors.
```

The failures are limited to six AMD files:

- E402 for imports deliberately placed after local path setup or module definitions
- F401 for three names intentionally re-exported from `triton_dist.layers.amd`
- F841 for two `grid` lambdas that are assigned but never used

### Expected behavior

The repository's pinned Ruff check should pass. Intentional late imports and public re-exports should be marked explicitly, while the two dead assignments can be removed.

Run the pinned Ruff command against python using python/pyproject.toml to reproduce the 21 errors. Inspect the six AMD files identified by Ruff, preserve the deliberate late imports and public re-exports explicitly, and remove the two unused grid assignments. Done means the pinned Ruff check reports no errors.

Written by the indexing model from the issue text.