show directory sizes

frontend/src/lib/components/file-browser/FileBrowserRowItem.svelte

@@ -255,7 +255,7 @@
                 class="shrink-0 px-4 h-full flex items-center justify-end text-xs text-text-secondary mono text-right tabular-nums font-medium border-r border-border-color/10"
                 style="width: {colWidths.size}px"
         >
-                {item.type === "directory" ? "" : formatSize(item.size)}
+			{formatSize(item.size)}
         </div>
 
         <!-- QUICK ACTIONS -->

frontend/src/lib/utils.ts

@@ -43,8 +43,9 @@ export function formatLocalDateTime(dateStr: string | null | undefined): string
  * Formats a byte count into a human-readable string (KB, MB, GB, TB).
  * (MEDIUM #28 — consolidated from 5+ duplicate implementations)
  */
-export function formatSize(bytes: number): string {
+export function formatSize(bytes: number | null | undefined): string {
     if (bytes === 0) return "0 B";
+    if (!bytes) return "—";
     const units = ["B", "KB", "MB", "GB", "TB"];
     let unitIndex = 0;
     let size = bytes;