Chat: handle aborted responses in assistant message cell UI

[x] In the following state, before we successfully fetched context, could we just remove the extra human message and return them to the original one? Otherwise it feels like the chat is left in a broken-ish state.
[x] Once we have an assistant message that has been aborted, can we not show the rating thumbs up/down
[x] can we add a paragraph in to say that the stream was stopped?
[x] If we could add this chat state to the Storybook scenarios too, that would be fantastic thanks!

Summary:

Add isAbortErrorOrSocketHangUp function to shared error utilities
Update AssistantMessageCell to handle aborted responses by displaying a message indicating the output stream was stopped
Ensure context focus actions are still shown for aborted responses
Update storybook with the aborted messages

Test plan

Updated Storybook with the expected behavior for aborted messages with and without assistant response: