kvm2: user guide, appendix column and section, architecture and README entries

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

README.md

@@ -160,6 +160,10 @@ Managed proxies as VMs on libvirt/KVM hosts you own. Full guide:
    size (`placement.machineType`) and an image (`placement.image`) — see
    [config/samples/proxy_kvm.yaml](config/samples/proxy_kvm.yaml).
 
+The `kvm2` provider uses the same Secret and the same block shape (`type: kvm2`,
+block `kvm2:`), so the steps above apply to it unchanged; its guide is
+[docs/kvm2-provider.md](docs/kvm2-provider.md).
+
 Cloud-init from a Secret: the Secret **must** carry the label
 `crawl.example.com/cloud-init: "true"` — the operator's cache only holds
 labelled Secrets, so an unlabelled one is invisible (the Proxy reports
@@ -187,6 +191,7 @@ can be two differently-configured instances of the same `gcp` type (see
 | `kubernetes` | A real Squid pod (`ubuntu/squid:6.6-24.04_edge` by default) in the same cluster the operator runs in | `image` (optional) | Needs no cloud account — local dev, CI, and the kind quickstart. Pods share the cluster's egress IP, so it exercises the full lifecycle but not distinct egress paths. |
 | `gcp` | A Compute Engine VM with an ephemeral external IP | `project` (required), `network`, `networkTag`, `diskSizeGb` | The real egress fleet. Deliberately uses only four API calls (Insert / Get / Delete / AggregatedList), all fire-and-forget: `Create` returns as soon as the operation is submitted and the reconciler discovers progress by polling `Get`. Auth is Application Default Credentials — workload identity in-cluster, `gcloud` ADC locally; no key-file plumbing. |
 | `kvm` | A libvirt VM on one of your own hypervisors, reached over SSH | `sshKeyFile`, `knownHostsFile` (unless `insecureIgnoreHostKey`), `machineTypes`, `hosts` (required); `images`, `diskSizeGb`, `vendorData`, `installGuestAgent` | Home-lab or on-prem egress. The base image is downloaded into each host's pool on first use; `Create` waits for the VM to start. See [docs/kvm-provider.md](docs/kvm-provider.md). |
+| `kvm2` | The same: a libvirt VM on one of your own hypervisors, reached over SSH | the same block shape as `kvm`, under `kvm2:` | The second-generation libvirt provider, built from the provider contract. Adds a child span per libvirt RPC, a pool-space precheck reported as quota (the reconciler waits instead of failing), SSH credentials re-read on every dial, and image downloads and health checks on connections of their own. It does not adopt `kvm`'s VMs. See [docs/kvm2-provider.md](docs/kvm2-provider.md). |
 
 ### Adding a provider