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/daemon/opencode.go

@@ -0,0 +1,18 @@
+package daemon
+
+import (
+	"context"
+
+	"banger/internal/model"
+	"banger/internal/opencode"
+)
+
+type opencodeCapability struct{}
+
+func (opencodeCapability) Name() string { return "opencode" }
+
+func (opencodeCapability) PostStart(ctx context.Context, d *Daemon, vm model.VMRecord, _ model.Image) error {
+	return opencode.WaitReady(ctx, d.logger, vm.Runtime.VSockPath, func(stage, detail string) {
+		vmCreateStage(ctx, stage, detail)
+	})
+}