add session stream channel documentation

mentat/session_stream.py

@@ -26,12 +26,30 @@ class StreamMessage:
 
 
 class SessionStream:
-    """Replaces `cprint` and `print`
+    """
+    Used to send and receive messages from the client.
+
+    Channels and their expected behavior (starred channels are sent by the client):
+
+    default: Any data sent to the client over this channel should be displayed. Valid kwargs: color, style]
+
+    *session_exit: Sent by the client, suggesting that the session should exit whenever possible.
+    client_exit: Sent by the server directly before shutting down. Client should shut down when received.
+
+    loading: Used to tell the client to display a loading bar. Valid kwargs: progress, terminate
+
+    input_request: Used to request input from the client (data unused). Valid kwargs: plain
+    *input_request:<message_id>: Sent by the client. The channel the response to an input_request is sent over.
+
+    edits_complete: A boolean sent when edits have been completed. True if any edits were accepted.
+
+    *completion_request: Sent by the client, asking for autocompletions for the given string.
+    completion_request:<message_id>: The response to the given completion request.
 
-    Stores message history for a Session and holds an in-memory message bus.
+    default_prompt: The prefilled prompt to show on next user input request. Should be additive and reset
+    after every input request. See TerminalClient for exact implementation.
 
-    Terminal and extension clients can read these messages and render them accordingly.
-    For the terminal, they would be rendered with `cprint`.
+    *interrupt: Sent by the client. Sent whenever client interrupts current work. Equivalent to ctrl-C
     """
 
     def __init__(self):