The column headers for the directory preview were a solid color, which
was conflicting with the translucent colors for the rest of the UI. I've
changed this to be more consistent. I've also updated a border color
that was conflicting with the rest of the UI.
The code blocks in the markdown preview were also solid colored and the
actions were causing the whole window UI to lose its transparency when
they were hovered over. This was due to it applying a backdrop-filter,
which breaks the window transparency. I've removed this blur and an
invalid color variable.
This also fixes the bottom margins for both blocks so there's more space
when scrolled all the way to the bottom of the block. Before, the
overlay scrollbars were obscuring the content.
