fix(documents): FolderBreadcrumb a11y — aria-hidden separators + aria-current

Match the existing src/components/ui/breadcrumb.tsx pattern: separator
chevrons are aria-hidden so screen readers don't announce them, and
the terminal segment (Root or current folder name) carries
aria-current="page" so SR users know which crumb is the current page.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/components/documents/folder-breadcrumb.tsx

@@ -47,15 +47,19 @@ export function FolderBreadcrumb({ selectedFolderId, onSelect }: FolderBreadcrum
       </button>
       {path.length === 0 && selectedFolderId === null ? (
         <>
-          <ChevronRight className="h-3.5 w-3.5" />
-          <span className="text-foreground">Root</span>
+          <ChevronRight className="h-3.5 w-3.5" aria-hidden="true" />
+          <span className="text-foreground" aria-current="page">
+            Root
+          </span>
         </>
       ) : null}
       {path.map((node, i) => (
         <span key={node.id} className="flex items-center gap-1">
-          <ChevronRight className="h-3.5 w-3.5" />
+          <ChevronRight className="h-3.5 w-3.5" aria-hidden="true" />
           {i === path.length - 1 ? (
-            <span className="text-foreground">{node.name}</span>
+            <span className="text-foreground" aria-current="page">
+              {node.name}
+            </span>
           ) : (
             <button
               type="button"