monitor: see unikernel VMs + use canonical container naming

Two drift-reporting bugs:
1. The monitor listed only the podman runtime, so unikernel VMs always
   showed observed=unknown (false drift). It now takes a ContainerLister
   and the agent passes a merged lister (containers + VMs), mirroring
   listAllContainers.
2. The monitor computed the lookup name as service+"-"+component, which
   is wrong when component==service (the name collapses to just the
   service, e.g. "uktest"/"mc-proxy"). It now uses the canonical
   naming.ContainerNameFor — extracted to a shared package so the agent
   and monitor can't disagree.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

internal/naming/naming.go

@@ -0,0 +1,37 @@
+// Package naming centralizes the container/VM naming convention shared by the
+// agent (which creates and reconciles containers) and the monitor (which looks
+// them up by name). Keeping it in one place prevents the two from disagreeing.
+package naming
+
+import "strings"
+
+// ContainerNameFor returns the expected container (or unikernel VM) name for a
+// service and component. For single-component services where the component
+// name equals the service name, the name is just the service name (e.g.,
+// "mc-proxy" not "mc-proxy-mc-proxy").
+func ContainerNameFor(service, component string) string {
+	if service == component {
+		return service
+	}
+	return service + "-" + component
+}
+
+// SplitContainerName splits a container name into service and component parts.
+// It checks known service names first to handle names like "mc-proxy" where a
+// naive split on "-" would produce the wrong result. If no known service
+// matches, it falls back to splitting on the first "-".
+func SplitContainerName(name string, knownServices map[string]bool) (service, component string) {
+	if knownServices[name] {
+		return name, name
+	}
+	for svc := range knownServices {
+		prefix := svc + "-"
+		if strings.HasPrefix(name, prefix) && len(name) > len(prefix) {
+			return svc, name[len(prefix):]
+		}
+	}
+	if i := strings.Index(name, "-"); i >= 0 {
+		return name[:i], name[i+1:]
+	}
+	return name, name
+}