fix: add state attribute to ToolCallRequest overrides (#6668)

Following https://github.com/langchain-ai/langchain/pull/34692

libs/prebuilt/langgraph/prebuilt/tool_node.py

@@ -121,6 +121,7 @@ class _ToolCallRequestOverrides(TypedDict, total=False):
     """Possible overrides for ToolCallRequest.override() method."""
 
     tool_call: ToolCall
+    state: Any
 
 
 @dataclass
@@ -170,8 +171,12 @@ class ToolCallRequest:
         This follows an immutable pattern, leaving the original request unchanged.
 
         Args:
-            **overrides: Keyword arguments for attributes to override. Supported keys:
-                - tool_call: Tool call dict with name, args, and id
+            **overrides: Keyword arguments for attributes to override.
+
+                Supported keys:
+
+                - tool_call: Tool call dict with `name`, `args`, and `id`
+                - state: Agent state (`dict`, `list`, or `BaseModel`)
 
         Returns:
             New ToolCallRequest instance with specified overrides applied.