Add real file loading: native file/folder picker + OS drag-and-drop, backed by real Rust commands (pick_files/pick_folder/expand_dropped_paths)

src/components/RenamePanel.css

@@ -120,6 +120,52 @@
   background: #28515a;
 }
 
+.load-menu {
+  position: relative;
+  display: inline-flex;
+}
+
+.load-menu-popup {
+  position: absolute;
+  bottom: calc(100% + 6px);
+  left: 0;
+  z-index: 10;
+  display: flex;
+  flex-direction: column;
+  min-width: 150px;
+  padding: 4px;
+  background: #16262d;
+  border: 1px solid var(--surface-deep);
+  border-radius: 10px;
+  box-shadow: 0 8px 24px rgba(0, 0, 0, 0.35);
+}
+
+.load-menu-popup button {
+  all: unset;
+  box-sizing: border-box;
+  padding: 8px 10px;
+  border-radius: 6px;
+  font-size: 12px;
+  color: var(--text);
+  cursor: pointer;
+  white-space: nowrap;
+}
+
+.load-menu-popup button:hover {
+  background: var(--surface-deep);
+}
+
+.list-empty-hint {
+  flex: 1;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  text-align: center;
+  padding: 24px;
+  color: var(--muted-text);
+  font-size: 12px;
+}
+
 .rename-actions {
   display: flex;
   flex-direction: column;