kvm2: config block, constructor registration, IDs, state mapping and classify

The kvm2 block reuses KVMConfig; validateKVM gains a block-name variant so
messages say kvm2. The package skeleton has a non-dialing New, strict
providerID parsing, the state table and a 34-row classify test.

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

internal/provider/config.go

@@ -22,6 +22,9 @@ type ProviderConfig struct {
 	Kubernetes *KubernetesConfig `json:"kubernetes,omitempty"`
 	GCP        *GCPConfig        `json:"gcp,omitempty"`
 	KVM        *KVMConfig        `json:"kvm,omitempty"`
+	// KVM2 is the same block shape as KVM, for the kvm2 provider type: one
+	// or more libvirt/KVM hypervisors reached over SSH.
+	KVM2 *KVMConfig `json:"kvm2,omitempty"`
 }
 
 // setBlocks names the type-specific blocks that are non-nil, so validate can
@@ -37,6 +40,9 @@ func (p ProviderConfig) setBlocks() []string {
 	if p.KVM != nil {
 		out = append(out, "kvm")
 	}
+	if p.KVM2 != nil {
+		out = append(out, "kvm2")
+	}
 	return out
 }
 
@@ -100,7 +106,7 @@ func (c *Config) validate() error {
 
 		prefix := fmt.Sprintf("providers[%d] %q", i, p.Name)
 		switch p.Type {
-		case "kubernetes", "gcp", "kvm":
+		case "kubernetes", "gcp", "kvm", "kvm2":
 		case "":
 			return fmt.Errorf("%s: type is required", prefix)
 		default:
@@ -120,6 +126,10 @@ func (c *Config) validate() error {
 			if err := validateKVM(prefix, p.KVM); err != nil {
 				return err
 			}
+		case "kvm2":
+			if err := validateKVMBlock(prefix, "kvm2", p.KVM2); err != nil {
+				return err
+			}
 		}
 	}
 	return nil