Studio: remove OpenEnv and other unused packages (#6585)

* Studio: drop OpenEnv and unused ExecuTorch/open_spiel install deps

* Studio: drop 8 more unused install deps from extras

* Studio: restore tomli<3.11 for kernels; tidy dep-cleanup comments and tests

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Studio: refresh scan-packages baseline for scipy _external + unsloth-zoo tests

scipy moved its vendored array_api_compat from scipy/_lib to
scipy/_external, so the four allowlisted array_api_compat __init__.py
entries stopped matching and resurfaced as unsuppressed CRITICAL
"Downloads and executes remote code" findings on all three pip
scan-packages shards (extras, hf-stack, studio). Add the _external
paths next to the existing _lib ones so both scipy layouts stay covered.

Allowlist two unsloth-zoo test-file false positives now present in the
hf-stack shard: tests/test_mlx_save_export_regressions.py (writes to
/tmp dropper) and tests/test_mlx_trainer_internals.py (obfuscation plus
exec/eval).

Drop nine stale entries for packages removed from the Studio
requirements and no longer in any shard closure (evaluate, pytest,
hypothesis, kgb, langid), confirmed absent via with-deps resolution of
all three shards.

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Daniel Han <danielhanchen@gmail.com>

studio/install_python_stack.py

@@ -1658,7 +1658,7 @@ def run(
 
 
 # Packages to skip on Windows (require special build steps)
-WINDOWS_SKIP_PACKAGES = {"open_spiel", "triton_kernels"}
+WINDOWS_SKIP_PACKAGES = {"triton_kernels"}
 
 # Packages to skip when torch is unavailable (Intel Mac GGUF-only mode).
 # These either *are* torch extensions or have unconditional
@@ -1675,7 +1675,6 @@ NO_TORCH_SKIP_PACKAGES = {
     "torchcodec",
     "torch-c-dlpack-ext",
     "openai-whisper",
-    "transformers-cfg",
     "librosa",
 }