Manage image artifacts and show VM create progress

Stop relying on ad hoc rootfs handling by adding image promotion, managed work-seed fingerprint metadata, and lazy self-healing for older managed images after the first create.

Rebuild guest images with baked SSH access, a guest NIC bootstrap, and default opencode services, and add the staged Void kernel/initramfs/modules workflow so void-exp uses a matching Void boot stack.

Replace the opaque blocking vm.create RPC with a begin/status flow that prints live stages in the CLI while still waiting for vsock health and opencode on guest port 4096.

Validate with GOCACHE=/tmp/banger-gocache go test ./... and live void-exp create/delete smoke runs.

internal/api/types.go

@@ -1,6 +1,10 @@
 package api
 
-import "banger/internal/model"
+import (
+	"time"
+
+	"banger/internal/model"
+)
 
 type Empty struct{}
 
@@ -24,6 +28,32 @@ type VMCreateParams struct {
 	NoStart           bool   `json:"no_start,omitempty"`
 }
 
+type VMCreateStatusParams struct {
+	ID string `json:"id"`
+}
+
+type VMCreateOperation struct {
+	ID        string          `json:"id"`
+	VMID      string          `json:"vm_id,omitempty"`
+	VMName    string          `json:"vm_name,omitempty"`
+	Stage     string          `json:"stage,omitempty"`
+	Detail    string          `json:"detail,omitempty"`
+	StartedAt time.Time       `json:"started_at,omitempty"`
+	UpdatedAt time.Time       `json:"updated_at,omitempty"`
+	Done      bool            `json:"done"`
+	Success   bool            `json:"success"`
+	Error     string          `json:"error,omitempty"`
+	VM        *model.VMRecord `json:"vm,omitempty"`
+}
+
+type VMCreateBeginResult struct {
+	Operation VMCreateOperation `json:"operation"`
+}
+
+type VMCreateStatusResult struct {
+	Operation VMCreateOperation `json:"operation"`
+}
+
 type VMRefParams struct {
 	IDOrName string `json:"id_or_name"`
 }