Wrap and space the empty-state placeholder in main pane

The centered placeholder ("Select a document" / "Not connected: ...")
had no width constraint, so long text rendered as a single over-wide,
cramped line. Constrain its width, center-align, enable word wrap, and
set lineHeight 1.3 so the message breathes.

ui/qml/Main.qml

@@ -246,12 +246,17 @@ ApplicationWindow {
 
             Label {
                 anchors.centerIn: parent
+                width: Math.min(parent.width - root.baseFontSize * 4,
+                                root.baseFontSize * 30)
                 visible: root.currentDoc === ""
                 text: orkClient.connected
                       ? qsTr("Select a document")
                       : qsTr("Not connected: %1").arg(orkClient.error)
                 color: theme.placeholderTextColor
                 font.pointSize: root.baseFontSize + 1
+                horizontalAlignment: Text.AlignHCenter
+                wrapMode: Text.WordWrap
+                lineHeight: 1.3
             }
         }
     }