## Problem

`omarchy.active-window` prints the focused window's title on **every** monitor's bar. On a
multi-monitor setup each bar names a window that only exists on one of them, so the title is
wrong on every screen except the one that actually holds the focused window.

There is no setting for this — the widget has to be replaced to get correct behaviour.

## Root cause

`shell/plugins/bar/widgets/ActiveWindow.qml:12`:

```qml
readonly property var toplevel: ToplevelManager.activeToplevel
```

`ToplevelManager.activeToplevel` is the compositor-global focused toplevel from the Wayland
foreign-toplevel protocol. `Bar.qml` builds one bar surface per monitor:

```qml
Variants {
  model: Quickshell.screens
  ...
}
```

Every surface therefore renders the same global value. The widget has no notion of which
output it is drawn on.

## Steps to reproduce

1. Two monitors, a window on each.
2. Focus a window on monitor A.
3. Monitor B's bar shows monitor A's window title.

## Suggested fix

Compare the bar surface's own output against the focused window's monitor and render only on
the match:

- the surface's screen: `root.QsWindow.window.screen.name`
- the window's monitor: Hyprland's toplevel list carries it, the Wayland handle does not, so
  match the two by object identity:

```qml
readonly property string toplevelScreenName: {
  if (!root.toplevel) return ""
  var values = Hyprland.toplevels.values
  for (var i = 0; i < values.length; i++) {
    if (values[i].wayland === root.toplevel)
      return values[i].monitor ? String(values[i].monitor.name || "") : ""
  }
  return ""
}
```

Then gate `visible` on `screenName === toplevelScreenName`. Reporting `implicitWidth: 0` when
hidden lets the bar slot collapse rather than sit empty.

I have this running locally and it behaves correctly on both outputs. Happy to open a PR if
the approach looks right.

## Related but distinct

There are open PRs fixing the same *class* of bug in the **workspaces** widget —
#8997, #8435 and #7243 all deal with `omarchy.workspaces` using global rather than
per-monitor state. This is the sibling bug in `omarchy.active-window`, which none of them
touch, and I could not find an existing report for it.

## System

```
omarchy          4.0.2-1
quickshell       0.3.1-1
qt6-declarative  6.11.2-1
hyprland         0.56.2-1
monitors         HDMI-A-1 1920x1080@60, DP-1 1920x1080@60
```