Split View does not account for 1px border

[yiliang114]

Reproduction steps:

1. Open https://vscode.dev/github/microsoft/vscode

2. Open a file and use command Split Editor Right

3. Look carefully at the dividing line of tab on the right.
   

4. The browser method can observe that the width of the border line is inconsistent when the first tab of the editor and the second tab are activated.
   
   

Version: 1.87.2
Commit: 863d258
User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/122.0.0.0 Safari/537.36
Embedder: vscode.dev

[benibenj]

This seems to be a Split View problem which also appears on desktop. The second element in the Split View sets the border between the two views with absolute positioning and does not account for any margin. This means the border is insider the view range and hence the view can draw under and on top of it. @joaomoreno