Implement transactional draft editing and client creation vertical slice

docs/PROJECT_LAYOUT.md

@@ -30,6 +30,8 @@ src/
   config.rs                # Application settings and path resolution
   domain.rs                # Clients, identities, address allocation/reservations, change states
   app.rs                   # Application operations and orchestration
+  app/
+    draft.rs               # Coordinated in-memory document, client-state, and vault drafts
   wireguard.rs             # Server configuration module boundary
   wireguard/
     document.rs            # Parsing and edits preserving original text
@@ -49,7 +51,8 @@ src/
 tests/
   config_preservation.rs   # Untouched server configuration remains identical
   commit_restore.rs        # Persistence, backups, restore, runtime isolation
-  client_lifecycle.rs      # Import, creation, delivery, deletion, state transitions
+  client_delivery.rs       # Client file delivery and lifecycle workflows
+  vault_import.rs          # Existing-client import and reconciliation workflows
   tui_workflow.rs          # Synthetic worker-level TUI workflows
   fixtures/                # Synthetic configuration and archive inputs
   support/