Back button when opening a tool or category from Smart Care

[weskcode]

What would you like?
A back button in the toolbar (plus Cmd+[) that takes you back to the screen you were just on.

Right now, when I'm on Smart Care and click into something, like a result row (System Junk, User Cache, etc.) or one of the tool cards (Space Explorer, Duplicate Finder, Protection, Performance), the detail pane switches to that screen. The only way back is to find Smart Care in the sidebar again. What I want after reviewing one area is to go back to the overview and open the next one.

It could work like the back button in Finder or System Settings: it sits in the toolbar, goes back one step, and is greyed out when there's nothing to go back to. Clicking something in the sidebar would still work the way it does now.

Why is this useful?
Smart Care works as a loop: scan, look at the results, open each one. Right now every time you open one there's no direct way back, so you end up going back and forth between the detail view and the sidebar. A back button fits that loop, and it's what Mac users expect from Finder and System Settings. It also makes the app easier to use from the keyboard.

Space Explorer already has a back chevron for moving between folders, so the app already does this in one place.

Alternatives considered

• The sidebar. It works, but it takes you to a fixed place in the app. It doesn't take you back to whatever you were just looking at.
• Breadcrumbs at the top of the detail view ("Smart Care > System Junk"). That would work too, but a back button adds less UI and is more standard on macOS.

From a quick look at main: DashboardView calls onNavigate, which goes to MainWindow.selectSection(_:) and replaces selectedSection, so no history is kept. Keeping a small stack of previous sections in MainWindow, adding to it in selectSection and going back through it from a toolbar chevron.left button, would probably be enough.