chore(documents): remove legacy /documents/files route + folder tree

The /documents/files page rendered a storagePath-prefix folder tree
disconnected from document_folders. Replaced by the unified hub
(Task 15). 301 redirect catches stray bookmarks. file-browser-store
repurposed to hold the document_folders.id selection.

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

src/components/search/command-search.tsx

@@ -1010,7 +1010,7 @@ function buildFlatRows(args: BuildFlatRowsArgs): FlatRow[] {
         icon: Folder,
         label: f.filename,
         sub: f.ownerLabel,
-        href: `/${portSlug}/documents/files`,
+        href: `/${portSlug}/documents`,
       });
     }
   }