test: guard EngineType against C++/Python drift

csrc/engine/scheduler.hpp and deepinfer/engine/engine_type.py define
EngineType twice, kept in sync only by a comment convention (the C++
side is not exposed through pybind). Parse the header and assert both
definitions match, so drift fails fast in CI instead of a Python enum
value silently meaning a different engine type to the C++ scheduler.

tests/engine/test_engine_type_consistency.py

@@ -0,0 +1,41 @@
+"""Guard against drift between the C++ and Python EngineType enums.
+
+csrc/engine/scheduler.hpp and deepinfer/engine/engine_type.py define the same
+enum twice (the C++ side is not exposed through pybind), and the two copies
+are only kept in sync by a comment convention. Parse the header and assert
+both definitions match, so an accidental drift fails fast in CI instead of a
+Python enum value silently being interpreted as a different engine type by
+the C++ scheduler.
+"""
+
+import re
+from pathlib import Path
+
+import pytest
+
+from deepinfer.engine.engine_type import EngineType
+
+pytestmark = [pytest.mark.ci, pytest.mark.ci_npu]
+
+HEADER = Path(__file__).resolve().parents[2] / "csrc" / "engine" / "scheduler.hpp"
+
+ENUM_RE = re.compile(r"enum\s+class\s+EngineType\s*:\s*int\s*\{(?P<body>.*?)\};", re.DOTALL)
+MEMBER_RE = re.compile(r"(\w+)\s*=\s*(-?\d+)")
+
+
+def cpp_engine_types() -> dict[str, int]:
+    source = HEADER.read_text(encoding="utf-8")
+    match = ENUM_RE.search(source)
+    assert match is not None, f"enum class EngineType not found in {HEADER}"
+    members = MEMBER_RE.findall(match.group("body"))
+    assert members, f"no members parsed from enum EngineType in {HEADER}"
+    return {name: int(value) for name, value in members}
+
+
+def test_engine_type_matches_cpp_definition() -> None:
+    cpp = cpp_engine_types()
+    py = {member.name: member.value for member in EngineType}
+    assert py == cpp, (
+        "EngineType definitions drifted between csrc/engine/scheduler.hpp and "
+        f"deepinfer/engine/engine_type.py:\n  C++:   {cpp}\n  Python: {py}"
+    )