fix overflow bug on bookmark widget when area is too small

[pantosaur]

I found a bug where I get the following panic when there are too many bookmarks to fit inside the UI area:

thread 'main' panicked at src/commands/bookmark.rs:121:20:
attempt to subtract with overflow
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

The y coordinate of the ratatui::layout::Rect becomes -1 at line 121

I also made sure to truncate the TuiMenu options field to the maximum length, apparently area.height as usize - 1, whenever it exceeds that value

[kamiyaa]

LGTM Thanks!