Fix: persist project folder hierarchy

Frontend/src/components/shell/ProjectSelector/ProjectSelector.module.scss

@@ -192,13 +192,61 @@
 
 .treeSectionLabel {
   @include text-caption;
-  margin: 0 0 var(--space-2);
+  margin: 0;
   padding: 0 var(--space-3);
   color: var(--color-text-subtle);
   text-transform: uppercase;
   letter-spacing: 0.04em;
 }
 
+.treeSectionHeader {
+	display: flex;
+	align-items: center;
+	justify-content: space-between;
+	gap: var(--space-2);
+	margin-bottom: var(--space-2);
+	padding-right: var(--space-1);
+}
+
+.treeControls {
+	display: inline-flex;
+	align-items: center;
+	gap: var(--space-1);
+	flex-wrap: wrap;
+	justify-content: flex-end;
+}
+
+.treeControlButton {
+	display: inline-flex;
+	align-items: center;
+	justify-content: center;
+	width: calc(var(--control-size-md) - var(--space-1));
+	height: calc(var(--control-size-md) - var(--space-1));
+	@include text-caption;
+	padding: 0;
+	border: 1px solid color-mix(in srgb, var(--color-border) 46%, transparent);
+	border-radius: var(--radius-pill);
+	background: color-mix(in srgb, var(--color-surface) 95%, transparent);
+	color: var(--color-text-muted);
+	transition:
+		border-color 160ms var(--easing-standard),
+		background 160ms var(--easing-standard),
+		color 160ms var(--easing-standard);
+}
+
+.treeControlButton:hover,
+.treeControlButton:focus-visible {
+	border-color: color-mix(in srgb, var(--color-border-strong) 56%, transparent);
+	background: var(--color-surface-hover);
+	color: var(--color-text);
+	outline: none;
+}
+
+.treeControlButton:disabled {
+	opacity: 0.45;
+	cursor: default;
+}
+
 .treeList {
   list-style: none;
   display: grid;