chore: import upstream snapshot with attribution

vllm/parser/engine/__init__.py

@@ -0,0 +1,17 @@
+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+"""
+Streaming parser engine framework for tool call and reasoning extraction.
+
+Instead of hand-rolling a parser for every model's tool-call / reasoning
+format, each format is declared as a ParserEngineConfig (terminals,
+states, and transitions) and a shared incremental engine handles
+streaming, ambiguity buffering, token-ID mapping, and delta computation.
+"""
+
+from vllm.parser.engine.events import EventType, SemanticEvent
+
+__all__ = [
+    "EventType",
+    "SemanticEvent",
+]