docs: remove context channel (#1824)

docs/docs/concepts/low_level.md

@@ -140,10 +140,6 @@ class State(TypedDict):
 
 In this example, we've used the `Annotated` type to specify a reducer function (`operator.add`) for the second key (`bar`). Note that the first key remains unchanged. Let's assume the input to the graph is `{"foo": 1, "bar": ["hi"]}`. Let's then assume the first `Node` returns `{"foo": 2}`. This is treated as an update to the state. Notice that the `Node` does not need to return the whole `State` schema - just an update. After applying this update, the `State` would then be `{"foo": 2, "bar": ["hi"]}`. If the second node returns `{"bar": ["bye"]}` then the `State` would then be `{"foo": 2, "bar": ["hi", "bye"]}`. Notice here that the `bar` key is updated by adding the two lists together.
 
-#### Context Reducer
-
-You can use `Context` channels to define shared resources (such as database connections) that are managed outside of your graph's nodes and excluded from checkpointing. The context manager provided to the Context channel is entered before the first step of the graph execution and exited after the last step, allowing you to set up and clean up resources for the duration of the graph invocation. Read this [how to](https://langchain-ai.github.io/langgraph/how-tos/state-context-key) to see an example of using the `Context` channel in your graph.
-
 ### Working with Messages in Graph State
 
 #### Why use messages?

docs/docs/how-tos/index.md

@@ -75,7 +75,6 @@ These guides show how to use different streaming modes.
 ## State Management
 
 - [Use Pydantic model as state](state-model.ipynb)
-- [Use a context object in state](state-context-key.ipynb)
 - [Have a separate input and output schema](input_output_schema.ipynb)
 - [Pass private state between nodes inside the graph](pass_private_state.ipynb)
 
@@ -85,7 +84,6 @@ These guides show how to use different streaming modes.
 - [How to visualize your graph](visualization.ipynb)
 - [How to add runtime configuration to your graph](configuration.ipynb)
 - [How to use a Pydantic model as your state](state-model.ipynb)
-- [How to use a context object in state](state-context-key.ipynb)
 - [How to add node retries](node-retries.ipynb)
 - [How to force function calling agent to structure output](react-agent-structured-output.ipynb)
 - [How to pass custom LangSmith run ID for graph runs](run-id-langsmith.ipynb)