Minor design tweaks for chat

[gregswinehart]

1. I'd love it if the container for the conversation ended above the text input at the bottom... It's quite noticeable when the scroll bar goes below where it seems like it should next to the text input:

2. Also, I think the chat container could use some padding on the left and right, to 1. let it breathe and 2. to avoid the scroll bar smooshing up next to it (especially noticeable when next to a code box.) Maybe .75rem on the left and right? Maybe even 1rem?