feat(documents): wire folder sidebar + breadcrumb + In-progress tab

Documents hub now opens with the folder tree on the left and a
breadcrumb on top. Folder selection is its own state — undefined =
"All", null = "Root only", string = specific folder. Filter pushes
through to /api/v1/documents via folderId query param.

Drops the "Signature-based only" pill — it defaulted to true and
silently hid informational documents, which confused new reps. With
folders the rep organises by location, not by signature-vs-not.

Adds an "In progress" hub tab covering status IN (draft, sent,
partially_signed) for the everyday "what's in flight" view.

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

src/lib/validators/documents.ts

@@ -72,6 +72,7 @@ export type CreateDocumentWizardInput = z.infer<typeof createDocumentWizardSchem
 
 export const documentsHubTabs = [
   'all',
+  'in_progress',
   'eoi_queue',
   'awaiting_them',
   'awaiting_me',