fix(opentrons-ai-client) fix textarea overlapping issue

[koji]

Overview

fix Textarea overlapping issue and fix auto scrolling.

attached the video to the ticket since I cannot upload the big video to Github.

close AUTH-435

Test Plan

• run the app
• send a few prompts

Changelog

• update height to fix the overlapping issue
• rename component name (ChatContainer -> MainContentContainer)

Review requests

Risk assessment

low

[shlokamin]

sorry if this is obvious, but why do we conditionally change styles if the role is user?

[koji]

the reason we need to use conditional here is that we don't display code hight lighter in user prompt.

oops, this shouldn't be in the PR.
#15308

I think we can do something like this.

<Markdown
            components={{
              div: undefined,
              ul: UnnumberedListText,
              h2: HeaderText,
              li: ListItemText,
              p: ParagraphText,
              a: ExternalLink,
              code: isUser ? undeifned : CodeText,
            }}
          >

[koji]

https://github.com/Opentrons/opentrons/pull/15308/files

I'm going to remove this conditional statement from the PR.