Bug - Horizontal scrollbar missing when response bubble overflows view area with left sidebar active

The current version (0.237.011) is missing the horizontal scrollbar at the bottom of the chat history window when the response expands past the defined viewable area.

Here's a picture of an overflowed conversation response with the left sidebar expanded (default site behavior). Note the two lines of text that continue offscreen but the lack of horizontal scrollbar to allow the user to view the full response or access the "Copy" button in the upper right corner of code blocks.

Currently I've asked users to workaround by hiding the left sidebar so that the viewable area can be expanded by expanding the whole browser window.

Reproduce the overflow in the chat history window with the left sidebar expanded and a response wider than the viewable area. Trace the chat history layout and overflow behavior from there; done means the horizontal scrollbar appears and users can view the full response and reach the Copy button in code blocks.

Written by the indexing model from the issue text.