fix(jetbrains): invalidate diff tree layout cache on folder toggle

A folder row hides its rolled-up badge while expanded, so its preferred
width now depends on expansion state. JTree only invalidates cached path
bounds on model changes, not on expand/collapse, so a collapsed folder could
keep its narrower expanded-state bounds and let the re-shown badge squeeze
the file name until an unrelated re-measure. Add a TreeExpansionListener that
invalidates the layout cache on toggle so the row re-measures immediately.

packages/kilo-jetbrains/frontend/src/main/kotlin/ai/kilocode/client/diff/KiloDiffEditorContent.kt

@@ -49,6 +49,7 @@ import com.intellij.ui.components.JBScrollPane
 import com.intellij.ui.treeStructure.Tree
 import com.intellij.util.concurrency.annotations.RequiresEdt
 import com.intellij.util.ui.JBUI
+import com.intellij.util.ui.tree.TreeUtil
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.Job
@@ -67,6 +68,8 @@ import javax.swing.JPanel
 import javax.swing.ScrollPaneConstants
 import javax.swing.JViewport
 import javax.swing.JTree
+import javax.swing.event.TreeExpansionEvent
+import javax.swing.event.TreeExpansionListener
 import javax.swing.tree.DefaultMutableTreeNode
 import javax.swing.tree.DefaultTreeModel
 import javax.swing.tree.TreeCellRenderer
@@ -439,6 +442,15 @@ private fun buildFileTree(files: List<DiffFileDto>): Tree {
         val node = path.lastPathComponent as? DefaultMutableTreeNode
         (node?.userObject as? Node)?.name.orEmpty()
     }
+    // A folder row hides its rolled-up badge while expanded, so its preferred width depends on
+    // expansion state. JTree only invalidates cached path bounds on model changes, not on
+    // expand/collapse, so a collapsed folder would keep its narrower expanded-state bounds and the
+    // re-shown badge would squeeze the name until an unrelated re-measure. Invalidate the layout
+    // cache on toggle so the row re-measures immediately.
+    tree.addTreeExpansionListener(object : TreeExpansionListener {
+        override fun treeExpanded(event: TreeExpansionEvent) = TreeUtil.invalidateCacheAndRepaint(tree.ui)
+        override fun treeCollapsed(event: TreeExpansionEvent) = TreeUtil.invalidateCacheAndRepaint(tree.ui)
+    })
     expandAll(tree)
     return tree
 }

packages/kilo-jetbrains/frontend/src/test/kotlin/ai/kilocode/client/diff/KiloDiffEditorContentTest.kt

@@ -144,6 +144,29 @@ class KiloDiffEditorContentTest : BasePlatformTestCase() {
         }
     }
 
+    fun `test folder row width tracks its badge visibility`() {
+        val parent = Disposer.newDisposable()
+        try {
+            val view = view(files(), parent)
+            val tree = components(view).filterIsInstance<Tree>().single()
+            val path = TreePath(folder(tree).path)
+
+            tree.expandPath(path)
+            val expanded = tree.getPathBounds(path)!!.width
+
+            // Collapsing re-shows the rolled-up badge, so the folder row's measured width must grow.
+            // This expansion-dependent width is why buildFileTree invalidates JTree's layout cache on
+            // toggle: a displayed tree caches path bounds across expand/collapse and would otherwise
+            // paint the row at its stale narrower width, squeezing the name.
+            tree.collapsePath(path)
+            val collapsed = tree.getPathBounds(path)!!.width
+
+            assertTrue("collapsed folder row must be wider to fit its badge", collapsed > expanded)
+        } finally {
+            Disposer.dispose(parent)
+        }
+    }
+
     fun `test leaf badge stays visible while its folder is expanded`() {
         val parent = Disposer.newDisposable()
         try {