Single Panel Detail Panel: File keeps closing

I've been using `singlePaneDetailPanel` for a bit now, and while I like the overall structure and approach, there are some issues that frustrated my experience. I imagine some are just small bugs in the preview, others maybe tweaks.

### 1 - Files keeps being closed
I want to quickly switch to files, check things, then revert to changes, and so on. Problem is: Files keeps closing. The reason is that "Files" switches to the individual file once I select it, so when I close, the Files tab is gone. While I can see the logic that "well it's opening one file", the fact the window is presented with the tree view on the side, it's effective how one would also browse files.

Steps:
1. Open the "Files" tab
2. Select one file
3. I'm done, close the file
4. Outcome: the files tree is now gone, and I've to re-add it as a tab.

An idea: barred larger flow fixes, one idea would simply be that if the file is pinned, when closed, it restores the empty "Files" selector instead of closing the tab.

### 2 - Changes show just one file
I appreciate the view with the full list of changes as a single list. For some things it's great. But when I want to see only one file, I keep accidentally scrolling too far in either direction, which is frustrating.

Steps:
1. Open the "Changes" view
2. Click on one specific file in the tree/list view
3. Outcome: scrolls to a file

An idea: provide a way to switch from a single list of all changes, to changes one-file-at-time so it can't scroll away (similar to how collapse all / expand all happens). Having a quick toggle like that would help switching view easily depending on the need / task.