[idea] Dim the panes behind a plugin popup pane, like the native modals

[akramdotsh]

idea / problem

When I open a plugin pane with --placement popup, it draws as a bordered,
centered float, but the panes behind it stay at full brightness. herdr's own
modals — settings, dialogs, keybind help — dim the background, so those read
as modals while a popup pane reads as just another floating pane.

requested change

Have popup plugin panes dim the background behind them the same way the native
modals do, so a --placement popup pane reads as a modal too. Happy to send a
small PR if you'd like it — I'll leave the product-direction call to you.

why you want this

I'm building a plugin whose status pane opens as a popup. The border and
centering already make it feel modal, but without the background dim it doesn't
quite read as one next to the native settings popup. Matching that behavior
would make popup-based plugin UIs feel consistent with the rest of herdr.

[korniychuk]

+1 — I hit the same thing from a different angle. I use three popup panes every day (a project picker, an app launcher and an agent-runs viewer), all opened with type = "popup". Every native modal (Settings, Help, Rename, …) dims what is behind it, so it is obvious where the focus is. A popup pane is the one modal surface that leaves the background at full brightness, and with a busy layout behind it I regularly have to look twice to see that the popup really owns the keyboard. Dimming the background the same way the native modals do would make popups feel consistent with the rest of the UI. Happy to test a build if that helps.

However, in my opinion, it's important to have the dim optional because if I open a regular application in a pop-up and want to see at the same time background tasks and task in pop-up, I don't want the background to be dim.

[akramdotsh]

@korniychuk Agreed. Optional dimming is the right call. For modal-feeling plugins (picker, launcher, status), matching native Settings/Help makes focus obvious. For a regular app in a popup, you still want to see what is running behind it.

Thanks for the concrete examples and for offering to test a build.