feat(ui): add scroll indicators to detail view

[fuleinist]

Summary

When the detail view (right panel) is scrollable, shows ▲ at top-right when scrolled down and ▼ at bottom-left when not at bottom.

Problem

The detailedResult window is scrollable with Shift+Arrow keys (issue #31), but there is no visual indication that the content is scrollable or what scroll position the user is at.

Solution

Add scroll position indicators:

• ▲ at top-right when scrolled down (not at top)
• ▼ at bottom-left when not at bottom

These only appear when (i.e., when content is actually scrollable).

Use case

Users can immediately see whether the detail view has more content above or below without having to try scrolling.

Testing

• Built successfully with go build
• The icons work in both Nerd Font and Unicode fallback modes

[Necrom4]

Thanks allot for giving a shot at this issue!
To be honest the positioning of these two arrows is not the best.

The goal of scrolling was because the window is too small to display the content fully, but in your solution the two arrows placed in the same space as there used to be content, meaning we're removing 2 full lines of information while there's plenty of free space, both to the exterior but also on the border (the arrows could be in the border line, like lazygit does it with it's scrollbar)

Also it would be better if the arrows are in the same side, it wasn't intuitive to try and find them.