Add vLLM v0.18.1 source tree with KV transfer abort fix

third_party/vllm/ now tracked in git for direct patch management.
Based on vLLM v0.18.1 release with one patch applied:

  vllm/v1/core/sched/scheduler.py:
    Replace fatal assert with graceful skip when KV transfer callback
    arrives for an already-aborted request during PD disaggregated serving.

Future vLLM modifications should be made directly in third_party/vllm/
and committed normally. The patches/ directory is kept as documentation
of what changed from upstream.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

third_party/vllm/tests/multimodal/media/test_base.py

@@ -0,0 +1,45 @@
+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+import pickle
+from pathlib import Path
+
+import pytest
+from PIL import Image
+
+from vllm.multimodal.media import MediaWithBytes
+
+pytestmark = pytest.mark.cpu_test
+
+ASSETS_DIR = Path(__file__).parent.parent / "assets"
+assert ASSETS_DIR.exists()
+
+
+def test_media_with_bytes_pickle_roundtrip():
+    """Regression test for pickle/unpickle of MediaWithBytes.
+
+    Verifies that MediaWithBytes can be pickled and unpickled without
+    RecursionError. See: https://github.com/vllm-project/vllm/issues/30818
+    """
+    original_image = Image.open(ASSETS_DIR / "image1.png").convert("RGB")
+    original_bytes = b"test_bytes_data"
+
+    wrapper = MediaWithBytes(media=original_image, original_bytes=original_bytes)
+
+    # Verify attribute delegation works before pickling
+    assert wrapper.width == original_image.width
+    assert wrapper.height == original_image.height
+    assert wrapper.mode == original_image.mode
+
+    # Pickle and unpickle (this would cause RecursionError before the fix)
+    pickled = pickle.dumps(wrapper)
+    unpickled = pickle.loads(pickled)
+
+    # Verify the unpickled object works correctly
+    assert unpickled.original_bytes == original_bytes
+    assert unpickled.media.width == original_image.width
+    assert unpickled.media.height == original_image.height
+
+    # Verify attribute delegation works after unpickling
+    assert unpickled.width == original_image.width
+    assert unpickled.height == original_image.height
+    assert unpickled.mode == original_image.mode