fix(molecule): stabilize default scenario networking

- serialize five-node Vagrant creation to avoid VirtualBox host-only races
- refresh and verify the primary neighbor mapping before convergence
- include interface MAC details in failure diagnostics

molecule/default/molecule.yml

@@ -3,6 +3,11 @@ dependency:
   name: galaxy
 driver:
   name: vagrant
+  # The Vagrant driver warns that parallel VirtualBox creation can cause
+  # platform issues. This five-node, mixed-distribution scenario is especially
+  # susceptible to stale host-only-network neighbor state when all guests are
+  # created concurrently.
+  parallel: false
 platforms:
   - name: control1
     box: generic/ubuntu2204