ci: add known_third_party to avoid pre-commit isort failure (#6292)

pyproject.toml

@@ -139,6 +139,13 @@ balanced_wrapping = true
 indent = "    "
 skip = ["build"]
 known_first_party = ["dynamo"]
+# isort may confuse what is 1st or 3rd library. e.g.
+# when dynamo/vllm/omni/xx.py import vllm, local isort may treat this `vllm` as first
+# party heuristically. This causes local sort differs from GitHub sort and pre-commit
+# failure. To mitigate 1) one can install 3rd party lib so that isort is aware of it,
+# 2) hardcode 3rd party lib here, 3) add "# isort: skip_file" to problematic files
+# as the last resort.
+known_third_party = ["vllm", "tensorrt_llm", "sglang"]
 
 [tool.pytest.ini_options]
 minversion = "8.0"