fix(documents-ui): a11y, mobile, realtime lift, type-safety, UI polish

- A2: lift useRealtimeInvalidation to DocumentsHub (covers all 3 render modes)
- B1-B4: aria-label, aria-pressed, aria-expanded, Lock SVG aria-hidden
- C1-C7: Sheet wrap for mobile sidebar, border axis fix, 44x44 tap targets
- Mobile Important: useMobileChrome title, FolderActionsMenu icon size, breadcrumb tap targets, signer email truncate
- Type-safety: ENTITY_TYPES guard, AggregatedSection discriminated union
- UI/UX: em-dash to colon in SigningDetailsDialog, Loading state normalize, StatusPill on HubRootView, view signing details as Button

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

src/components/documents/folder-breadcrumb.tsx

@@ -35,12 +35,12 @@ export function FolderBreadcrumb({ selectedFolderId, onSelect }: FolderBreadcrum
   return (
     <nav
       aria-label="Folder breadcrumb"
-      className="flex items-center gap-1 text-sm text-muted-foreground"
+      className="flex flex-wrap items-center gap-1 text-sm text-muted-foreground"
     >
       <button
         type="button"
         onClick={() => onSelect(undefined)}
-        className="flex items-center gap-1 hover:text-foreground"
+        className="flex min-h-[44px] items-center gap-1 py-2 hover:text-foreground"
       >
         <Home className="h-3.5 w-3.5" />
         <span>All</span>
@@ -64,7 +64,7 @@ export function FolderBreadcrumb({ selectedFolderId, onSelect }: FolderBreadcrum
             <button
               type="button"
               onClick={() => onSelect(node.id)}
-              className="hover:text-foreground"
+              className="flex min-h-[44px] items-center py-2 hover:text-foreground"
             >
               {node.name}
             </button>