사이드바에 트리 구조 폴더 기능 추가

src/renderer/style.css

@@ -423,6 +423,55 @@ footer span { font-size: 11px; color: var(--muted); }
   object-fit: contain;
 }
 
+/* ── 파일 탐색기 트리 ── */
+.tree-root { padding: 6px 0; }
+
+.tree-node { display: flex; flex-direction: column; }
+
+.tree-row {
+  display: flex; align-items: center; gap: 5px;
+  padding: 3px 8px 3px 0;
+  border-radius: 6px;
+  cursor: pointer;
+  user-select: none;
+  color: var(--text);
+  font-size: 12.5px;
+  transition: background .1s;
+  position: relative;
+}
+.tree-row:hover { background: rgba(255,255,255,.05); }
+.tree-row.active {
+  background: rgba(124,106,247,.18);
+  color: #d0c8ff;
+}
+
+.tree-chevron {
+  width: 16px; height: 16px;
+  display: flex; align-items: center; justify-content: center;
+  flex-shrink: 0; color: var(--muted);
+  transition: transform .15s;
+}
+.tree-chevron.open { transform: rotate(90deg); }
+.tree-chevron svg { display: block; }
+
+.tree-icon {
+  width: 16px; height: 16px;
+  display: flex; align-items: center; justify-content: center;
+  flex-shrink: 0;
+}
+.tree-icon svg { display: block; }
+
+.tree-label {
+  flex: 1; overflow: hidden; text-overflow: ellipsis; white-space: nowrap;
+  line-height: 1.4;
+}
+
+.tree-children {
+  padding-left: 16px;
+  border-left: 1px solid rgba(255,255,255,.05);
+  margin-left: 15px;
+}
+
 /* ── 토스트 ── */
 #toast {
   position: fixed; bottom: 40px; left: 50%;