Replace 'x' action with "Edit" in chat

[kkbrooks]

Problem

• The "x" action on the previous messages doesn't clearly set expectations for what happens when you click the button

Goals

• Update the UI without adding unnecessary complexity or new concepts
• Allow users to redirect the conversation in a new direction

Notes

• This issue has been updated to focus on editing UX first, then we'll reassess options for checkpoint

[jo-oikawa]

I'd like to propose splitting this into two issues: 1) replacing the "x" action (which I think we have a more clear solution for) and 2) replacing the undo-redo (which needs more discussion).

[jo-oikawa]

Updating name/description to focus on first bullet mentioned, "The "x" action on the previous messages doesn't clearly set expectations for what happens when you click the button"