fix(kcm): stop layout card button flicker on hover (#235)

The flicker had two cooperating causes:

1. The ToolButtons toggled `visible:` inside a right-anchored Row,
   causing leftward geometry reflow that shifted button positions —
   creating an unstable hover boundary (worse on left-side cards).

2. `ToolTip.visible: hovered` with no delay opened a tooltip popup
   instantly.  On some compositors the popup window momentarily steals
   pointer focus, flipping `hovered` false for one frame → tooltip
   hides → `hovered` true → loop.

Fix both layers:
- Wrap each ToolButton in a fixed-size Item so the Row's width never
  changes when buttons show/hide (eliminates geometry reflow)
- Add ToolTip.delay (standard KDE delay) to break the tooltip
  feedback loop on affected compositors
- Guard ToolTip.visible with && visible for safety

Co-Authored-By: claude-flow <ruv@ruv.net>

Author: fuddlesworth

kcm/ui/tabs/LayoutGridDelegate.qml

@@ -188,33 +188,46 @@ Item {
                     spacing: 0
 
                     // Auto-assign toggle (hidden for autotile — the tiling engine manages those)
-                    ToolButton {
+                    // Wrapped in fixed-size Item so the Row's width never changes when
+                    // the button shows/hides — prevents leftward geometry reflow that
+                    // destabilizes hover on some compositors.
+                    Item {
                         width: Kirigami.Units.iconSizes.small + Kirigami.Units.smallSpacing
                         height: width
-                        padding: 0
-                        visible: root.modelData.isAutotile !== true && (root.isHovered || root.modelData.autoAssign === true)
-                        icon.name: root.modelData.autoAssign === true ? "window-duplicate" : "window-new"
-                        icon.width: Kirigami.Units.iconSizes.small
-                        icon.height: Kirigami.Units.iconSizes.small
-                        icon.color: root.modelData.autoAssign === true ? Kirigami.Theme.textColor : Kirigami.Theme.disabledTextColor
-                        onClicked: root.kcm.setLayoutAutoAssign(root.modelData.id, !(root.modelData.autoAssign === true))
-                        ToolTip.visible: hovered
-                        ToolTip.text: root.modelData.autoAssign === true ? i18n("Auto-assign enabled: new windows fill empty zones. Click to disable.") : i18n("Click to auto-assign new windows to empty zones")
+
+                        ToolButton {
+                            anchors.fill: parent
+                            padding: 0
+                            visible: root.modelData.isAutotile !== true && (root.isHovered || root.modelData.autoAssign === true)
+                            icon.name: root.modelData.autoAssign === true ? "window-duplicate" : "window-new"
+                            icon.width: Kirigami.Units.iconSizes.small
+                            icon.height: Kirigami.Units.iconSizes.small
+                            icon.color: root.modelData.autoAssign === true ? Kirigami.Theme.textColor : Kirigami.Theme.disabledTextColor
+                            onClicked: root.kcm.setLayoutAutoAssign(root.modelData.id, !(root.modelData.autoAssign === true))
+                            ToolTip.text: root.modelData.autoAssign === true ? i18n("Auto-assign enabled: new windows fill empty zones. Click to disable.") : i18n("Click to auto-assign new windows to empty zones")
+                            ToolTip.delay: Kirigami.Units.toolTipDelay
+                            ToolTip.visible: hovered && visible
+                        }
                     }
 
                     // Visibility toggle
-                    ToolButton {
+                    Item {
                         width: Kirigami.Units.iconSizes.small + Kirigami.Units.smallSpacing
                         height: width
-                        padding: 0
-                        visible: root.isHovered || root.modelData.hiddenFromSelector === true
-                        icon.name: root.modelData.hiddenFromSelector ? "view-hidden" : "view-visible"
-                        icon.width: Kirigami.Units.iconSizes.small
-                        icon.height: Kirigami.Units.iconSizes.small
-                        icon.color: root.modelData.hiddenFromSelector ? Kirigami.Theme.disabledTextColor : Kirigami.Theme.textColor
-                        onClicked: root.kcm.setLayoutHidden(root.modelData.id, !root.modelData.hiddenFromSelector)
-                        ToolTip.visible: hovered
-                        ToolTip.text: root.modelData.hiddenFromSelector ? i18n("Hidden from zone selector. Click to show.") : i18n("Visible in zone selector. Click to hide.")
+
+                        ToolButton {
+                            anchors.fill: parent
+                            padding: 0
+                            visible: root.isHovered || root.modelData.hiddenFromSelector === true
+                            icon.name: root.modelData.hiddenFromSelector ? "view-hidden" : "view-visible"
+                            icon.width: Kirigami.Units.iconSizes.small
+                            icon.height: Kirigami.Units.iconSizes.small
+                            icon.color: root.modelData.hiddenFromSelector ? Kirigami.Theme.disabledTextColor : Kirigami.Theme.textColor
+                            onClicked: root.kcm.setLayoutHidden(root.modelData.id, !root.modelData.hiddenFromSelector)
+                            ToolTip.text: root.modelData.hiddenFromSelector ? i18n("Hidden from zone selector. Click to show.") : i18n("Visible in zone selector. Click to hide.")
+                            ToolTip.delay: Kirigami.Units.toolTipDelay
+                            ToolTip.visible: hovered && visible
+                        }
                     }
 
                 }