Resize handlers position is wrong for more than 2 panels in one branch

[artaommahe]

Describe the bug Having a gap between groups and visible resize handlers (replit theme e.g.), the position of these handlers is wrong if there is more than 2 panels in one direction

To Reproduce

Steps to reproduce the behavior:

1. Go to https://dockview.dev/demo/?theme=dockview-theme-replit
2. Set the gap to 20px
3. Move panels so there is more than 2 in one direction (within the same branch)
4. See that resize handlers are off

Expected behavior Handlers position is correct for any amount of panels in one branch

Screenshots 8 panels

3 panels

Desktop (please complete the following information):

• Browser: Chrome
• Version: Version 127.0.6533.89 (Official Build) (arm64)

Additional context Add any other context about the problem here.

[mathuo]

Seems to be issues with the position of the first and last resize handle containers when gap > 0. Additionally there are some issues with gaps when some panels are hidden using setVisible(false) which @RayJason has raised a partial PR fix.

I will combine both issues into a fix for the branch assoicated with this issue.

[mathuo]

Fixed in 1.16.0