refactor: read TORCH_GROUP directly in smoke tests, drop SMOKE_TEST_TORCH_GROUP

Now that the Makefile exports TORCH_GROUP unconditionally, the
smoke-test-specific SMOKE_TEST_TORCH_GROUP env var was redundant
indirection. ci/nox/noxfile.py reads TORCH_GROUP directly, and
`make test-smoke` no longer needs to translate the Makefile variable
into a differently-named env var for the nox subprocess.

Author: guru-desh

Makefile

@@ -250,7 +250,7 @@ test-slow:
 test-smoke:
 	@$(call use_env,VENV) && \
 	echo "Running smoke tests..." && \
-	SMOKE_TEST_TORCH_GROUP=$(TORCH_GROUP) uv run --no-sync --active nox -f $(MAKEFILE_DIR)ci/nox/noxfile.py -s smoke_tests -- $(PYTEST_ARGS) && \
+	uv run --no-sync --active nox -f $(MAKEFILE_DIR)ci/nox/noxfile.py -s smoke_tests -- $(PYTEST_ARGS) && \
 	echo "All smoke tests passed!"
 
 # Run tests on lowest supported PyTorch version (pass PYTEST_ARGS for custom flags)

ci/nox/noxfile.py

@@ -35,15 +35,16 @@
 options.error_on_missing_interpreters = True
 
 # Pins the torch minor version smoke tests install, one of the torch_2_*
-# dependency groups in pyproject.toml. Set by the CI matrix (ci.yaml) so each
-# job tests a different torch version; defaults to the newest supported.
-SMOKE_TEST_TORCH_GROUP = os.environ.get("SMOKE_TEST_TORCH_GROUP", "torch_2_11")
+# dependency groups in pyproject.toml — TORCH_GROUP is the project-wide
+# source of truth (see Makefile), exported by `make test-smoke` and set per
+# job by the CI matrix (ci.yaml); defaults to the newest supported.
+TORCH_GROUP = os.environ.get("TORCH_GROUP", "torch_2_11")
 
 
 @session(
     python=get_supported_python_versions(),
     uv_extras=["coreai"],
-    uv_groups=["test", SMOKE_TEST_TORCH_GROUP],
+    uv_groups=["test", TORCH_GROUP],
 )
 def smoke_tests(session: Session) -> None:
     """Smoke test the package build and coreai_opt imports and basic functionality.