S15: sm-leaf health HTTP, verae.sm.* acks, systemd unit

Loopback GET /health, nats-leaf:// rewrite, subject request-reply tests.
Do not replace pfc-py-admin. NpeRequired stays on the package surface.

go/internal/leaf/leaf.go

@@ -2,8 +2,12 @@
 package leaf
 
 import (
+	"encoding/json"
 	"errors"
+	"log"
+	"net/http"
 	"net/url"
+	"strings"
 	"time"
 
 	natsserver "github.com/nats-io/nats-server/v2/server"
@@ -16,11 +20,17 @@ type Node struct {
 	nc *nats.Conn
 }
 
+// ParseHub rewrites nats-leaf:// to nats:// then parses the URL.
+func ParseHub(hub string) (*url.URL, error) {
+	raw := strings.Replace(hub, "nats-leaf://", "nats://", 1)
+	return url.Parse(raw)
+}
+
 // Start binds 127.0.0.1:0 and optionally leaf-connects to hub.
 func Start(hub string) (*Node, error) {
 	opts := &natsserver.Options{Host: "127.0.0.1", Port: -1}
 	if hub != "" {
-		u, err := url.Parse(hub)
+		u, err := ParseHub(hub)
 		if err != nil {
 			return nil, err
 		}
@@ -40,17 +50,61 @@ func Start(hub string) (*Node, error) {
 		return nil, err
 	}
 	n := &Node{ns: ns, nc: nc}
-	if _, err := n.nc.Subscribe("verae.sm.send", func(msg *nats.Msg) {
-		if msg.Reply != "" {
-			_ = n.nc.Publish(msg.Reply, []byte(`{"accepted":true}`))
-		}
-	}); err != nil {
+	if err := n.subscribe(); err != nil {
 		n.Shutdown()
 		return nil, err
 	}
 	return n, nil
 }
 
+func (n *Node) subscribe() error {
+	ack := func(msg *nats.Msg, body []byte) {
+		if msg.Reply != "" {
+			_ = n.nc.Publish(msg.Reply, body)
+		}
+	}
+	if _, err := n.nc.Subscribe("verae.sm.send", func(msg *nats.Msg) {
+		// Passthrough: do not log ciphertext.
+		ack(msg, []byte(`{"accepted":true}`))
+	}); err != nil {
+		return err
+	}
+	if _, err := n.nc.Subscribe("verae.sm.dead", func(msg *nats.Msg) {
+		ack(msg, []byte(`{"queued":true}`))
+	}); err != nil {
+		return err
+	}
+	if _, err := n.nc.Subscribe("verae.sm.error", func(msg *nats.Msg) {
+		ack(msg, []byte(`{"emitted":true}`))
+	}); err != nil {
+		return err
+	}
+	if _, err := n.nc.Subscribe("verae.sm.log.summary", func(msg *nats.Msg) {
+		var hdr map[string]any
+		_ = json.Unmarshal(msg.Data, &hdr)
+		log.Printf("sm-summary code=%v lookup=%v class=%v", hdr["error_code"], hdr["lookup_id"], hdr["dest_class"])
+		ack(msg, []byte(`{"logged":true}`))
+	}); err != nil {
+		return err
+	}
+	return nil
+}
+
+// HealthHandler is the loopback JSON health mux (does not expose NATS).
+func HealthHandler() http.Handler {
+	mux := http.NewServeMux()
+	mux.HandleFunc("/health", func(w http.ResponseWriter, _ *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		_, _ = w.Write([]byte(`{"ok":true,"service":"sm-leaf"}`))
+	})
+	return mux
+}
+
+// ServeHealth binds a loopback health listener (does not expose NATS).
+func ServeHealth(addr string) error {
+	return http.ListenAndServe(addr, HealthHandler())
+}
+
 // Addr is the in-process client URL.
 func (n *Node) Addr() string { return n.ns.ClientURL() }