fix(ui): toolbars collapsed width glitch

   - The collapsed toolbar width logic was already shrinking the content area.
   - But the VisWindow title label still kept its full text, so the window pref width stayed title-driven on initial render and in auto-collapse mode.

   I fixed it in core/src/main/kotlin/com/github/alfu32/sketch/ui/SketchUiOverlay.kt.

   - CollapsibleWindow now stores its base title and can switch to a compact-title mode
   - when a toolbar is auto-collapsed:
       - the title text is set to ""
   - when expanded:
       - the full title is restored

   That makes the collapsed window width depend on the visible button, not on the title text.

Author: alferio

core/src/main/kotlin/com/github/alfu32/sketch/ui/SketchUiOverlay.kt

@@ -171,7 +171,9 @@ class SketchUiOverlay(
         private val fixedHeight: Float? = null,
         showCloseButton: Boolean = true
     ) : com.kotcrab.vis.ui.widget.VisWindow(title, true) {
+        private val baseTitle = title
         private var collapsed = false
+        private var toolbarCompactTitle = false
 
         init {
             isMovable = true
@@ -194,6 +196,15 @@ class SketchUiOverlay(
             isVisible = false
         }
 
+        fun setToolbarCompactTitle(compact: Boolean) {
+            if (toolbarCompactTitle == compact) {
+                return
+            }
+            toolbarCompactTitle = compact
+            getTitleLabel().setText(if (compact) "" else baseTitle)
+            invalidateHierarchy()
+        }
+
         fun setCollapsedState(value: Boolean) {
             if (collapsed == value) {
                 return
@@ -1762,6 +1773,7 @@ class SketchUiOverlay(
         val window = binding.window
         val oldX = window.x
         val oldTop = window.y + window.height
+        window.setToolbarCompactTitle(!expanded)
         binding.expanded = expanded
         binding.visibleButtonIndex = visibleButtonIndex
         binding.slots.forEachIndexed { index, slot ->