This PR fixes two issues with regards to markdown codeblocks rendered in
tool call input and output content display:
- the JSON code snippets weren't properly indented
- codeblocks weren't being rendered in unique containers; e.g., if you
hovered one scrollbar, all of them would also be hovered, even though
horizontal scrolling itself worked properly

Here's the end result:


https://github.com/user-attachments/assets/3d6daf64-0f88-4a16-a5a0-94998c1ba7e2

Release Notes:

- agent: Fix scrollbar and JSON indentation for tool call input/output
content's markdown codeblocks.