chore: replace deprecated EnvironmentError alias with OSError (ruff UP024)

[alexzhu0]

Summary

Ruff rule UP024 flags uses of the EnvironmentError alias. Since Python 3.3, EnvironmentError is OSError — same class object, EnvironmentError is OSError returns True. The alias is stylistically redundant.

>>> EnvironmentError is OSError
True

8 raise EnvironmentError(...) sites across 4 files, all in configuration / environment-setup code paths.

 def _require(val: Optional[str], label: str) -> None:
     if not val:
-        raise EnvironmentError(f"Missing required configuration: {label}")
+        raise OSError(f"Missing required configuration: {label}")

Caller compatibility

No except EnvironmentError clauses exist anywhere in the repo (grep -rn "except EnvironmentError" --include='*.py' . — zero hits outside generated code), so caller semantics are unchanged. And even if any did appear, they would continue to catch the raised exception because EnvironmentError is OSError.

Files

File	Sites
m_flow/adapters/graph/get_graph_adapter.py	2
m_flow/adapters/vector/create_vector_engine.py	3
m_flow/context_global_variables.py	2
m_flow/shared/files/utils/get_file_content_hash.py	1

4 files, +9 / −9 (one trailing docstring reference updated by hand for consistency).

Verification

$ ruff check . --exclude 'm_flow/baml_client' --exclude 'm_flow-frontend' --select UP024
All checks passed!

$ for f in <each touched file>; do uv run python -c "import ast; ast.parse(open('$f').read())"; done
# clean across all 4 files

$ grep -rn "except EnvironmentError" --include='*.py' . | grep -v baml_client
# (no output — zero call sites catch the aliased form)

No behavior change. Generated code under m_flow/baml_client/ is untouched.

I affirm that all code in every commit of this pull request conforms to the terms of the M-flow Developer Certificate of Origin