chore: update graphai docs

Author: aurelio-bot

docs.json

@@ -246,4 +246,4 @@
       "youtube": "https://www.youtube.com/@jamesbriggs"
     }
   }
-}
+}

graphai/client-reference/callback.mdx

@@ -24,6 +24,20 @@ conversation/session ID could be used.
 - `params` (`dict[str, Any] | None`): The parameters associated with the event, such as tool call parameters
 or event metadata.
 
+#### encode
+
+```python
+def encode(charset: str = "utf-8") -> bytes
+```
+
+Encodes the event as a JSON string, important for compatability with FastAPI
+
+and starlette.
+
+**Arguments**:
+
+- `charset` (`str`): The character set to use for encoding the event.
+
 ## Callback Objects
 
 ```python

graphai/user-guide/faqs.mdx

@@ -0,0 +1,33 @@
+
+## TypeError: object dict can't be used in 'await' expression
+
+This is a common mistake when defining the graph. The internals of `graphai` expect _all_ nodes to be defined with `async def`. When defining a node with `def` we will see this error:
+
+```
+Traceback (most recent call last):
+  File "/app/.venv/lib/python3.13/site-packages/graphai/graph.py", line 351, in execute
+    output = await current_node.invoke(input=state, state=self.state)
+             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+  File "/app/.venv/lib/python3.13/site-packages/graphai/nodes/base.py", line 152, in invoke
+    out = await instance.execute(**input)
+          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+  File "/app/.venv/lib/python3.13/site-packages/graphai/nodes/base.py", line 74, in execute
+    return await func(**params_dict)  # Pass only the necessary arguments
+           ^^^^^^^^^^^^^^^^^^^^^^^^^
+TypeError: object dict can't be used in 'await' expression
+```
+
+The solution is to always define nodes using `async def`. For example:
+
+```python
+
+# WRONG:
+@node
+def my_node(input: dict) -> dict:
+    return {"output": "Hello, world!"}
+
+# DO THIS INSTEAD:
+@node
+async def my_node(input: dict) -> dict:
+    return {"output": "Hello, world!"}
+```