island: fix three defects found by actually loading the shell

The island had never been load-tested. All three were fatal or noisy and
none were visible by reading.

StyledToolTip takes `text`, not `content`. Two occurrences, each one a
hard "Cannot assign to non-existent property" that failed the entire
module chain up to shell.qml — the bar would not have come back.

The provider-health tooltip could never have shown even once fixed: a
MaterialSymbol has no `hovered`, and our own StyledToolTip fix treats a
non-hoverable parent as never-show. That block exists specifically so an
unavailable provider is not mistaken for "no sessions", so a tooltip was
the wrong carrier. Stated visibly now.

Island read root.QsWindow.window through a non-optional access; inside a
Loader the attached object is not resolved at construction and it threw.

Revealer takes implicitHeight from childrenRect, so anchoring its child
to its own centre closes a cycle once it sits in a Loader. ii-base hid it
by letting the layout drive the Revealer height directly.

Verified: qs -c souveraine reaches "Configuration Loaded" with no warning
naming any of these files.

surfaces/quickshell/modules/ii/bar/BarContent.qml

@@ -266,12 +266,16 @@ Item { // Bar content region
 
     Component {
         id: pomodoroComp
+        // The child is deliberately NOT anchored to the Revealer's centre.
+        // Revealer takes implicitHeight from childrenRect, so a child anchored
+        // to its parent closes a real cycle once the Revealer sits in a Loader
+        // (implicitHeight -> height -> child.y -> childrenRect -> ...). ii-base
+        // hid it by letting the layout drive the Revealer's height directly.
+        // The indicator has a fixed implicitHeight and the Loader carries
+        // Layout.alignment, so it centres without the anchor.
         Revealer {
             reveal: TimerService.pomodoroRunning
-            Layout.fillHeight: true
-            PomodoroBarIndicator {
-                anchors.verticalCenter: parent.verticalCenter
-            }
+            PomodoroBarIndicator {}
         }
     }