fix(host): bring up VMware host stack at boot via native systemd units

Build VMs stopped starting after a reboot into a new kernel: vmmon/vmnet
were left unloaded and vmnet1/vmnet8 (DHCP/NAT) never came up, so
vmware-vmx died (status=237/KEYRING) and clones got no IP. Root cause:
the LSB->systemd sysv-generated vmware.service intermittently fails to
generate at early boot ("systemd-sysv-generator: Cannot find unit
vmware.service"), and the existing module-rebuild guard only builds the
modules -- it never loads them or starts vmnet networking.

Add a native vmware-host.service that runs `/etc/init.d/vmware start`
(loads vmmon/vmci + brings up vmnet), ordered after the rebuild guard,
and mask the flaky sysv vmware.service so the native unit is the sole
owner. Provisioned by scripts/install-vmware-host-services.sh and wired
into setup-host-linux.sh (new step 8/9). VMware ships no native unit and
no kernel postinst hook, so this native wrapper around VMware's own
tools is the reliable boot path.

Verified: linked clone boots and gets a vmnet8 DHCP IP.

docs/RUNBOOK-PhaseC.md

@@ -557,5 +557,6 @@ original `.ps1` scripts remain in `scripts/archived/`.
 | `bench run` round FAIL: orphan   | Clone was not destroyed                 | `ci vm cleanup`; check vmrun and `/var/lib/ci/build-vms`                                |
 | WinRM jobs drop at concurrency 4 | Known instability (TODO §3.6)           | Use `--concurrency 3`                                                                   |
 | IP-acquire timeout (Linux)       | vmnet8 DHCP wedged                      | `sudo systemctl restart vmware-networks`                                                |
-| `vmrun` "operation was canceled" | vmmon/vmnet unbuilt after a kernel bump | `sudo vmware-modconfig --console --install-all` (or reboot; the systemd guard rebuilds) |
+| `vmrun` "operation was canceled" | vmmon/vmnet unbuilt after a kernel bump | `sudo vmware-modconfig --console --install-all` (or reboot; `vmware-modules-rebuild.service` rebuilds) |
+| VMs won't start after a reboot — no `/dev/vmnet*`, `vmware-vmx` dies `status=237/KEYRING` | Host stack didn't come up at boot: `vmmon` unloaded + vmnet DHCP/NAT down (the flaky sysv `vmware.service` failed to generate — `systemd-sysv-generator: Cannot find unit vmware.service`) | `sudo systemctl start vmware-host.service`, then confirm it's enabled. Provisioned by `scripts/install-vmware-host-services.sh` — see [deploy/systemd](../deploy/systemd/README.md#servizi-vmware-host-prerequisito-avvio-vm) |
 | `ci: command not found`          | Alias not loaded                        | `source ~/.bashrc`, or re-run [§0.2](#02-install-the-ci-alias)                          |