Harden process ring buffer and daemon/health shutdown behavior

buffer.go

@@ -19,6 +19,10 @@ type RingBuffer struct {
 //
 //	rb := process.NewRingBuffer(256)
 func NewRingBuffer(size int) *RingBuffer {
+	if size <= 0 {
+		size = 1
+	}
+
 	return &RingBuffer{
 		data: make([]byte, size),
 		size: size,

daemon.go

@@ -164,7 +164,9 @@ func (d *Daemon) Stop() error {
 
 	// Auto-unregister
 	if d.opts.Registry != nil {
-		_ = d.opts.Registry.Unregister(d.opts.RegistryEntry.Code, d.opts.RegistryEntry.Daemon)
+		if err := d.opts.Registry.Unregister(d.opts.RegistryEntry.Code, d.opts.RegistryEntry.Daemon); err != nil {
+			errs = append(errs, core.E("daemon.stop", "registry", err))
+		}
 	}
 
 	d.running = false

health.go

@@ -104,10 +104,17 @@ func (h *HealthServer) Start() error {
 
 // Stop gracefully shuts down the health server.
 func (h *HealthServer) Stop(ctx context.Context) error {
-	if h.server == nil {
+	h.mu.Lock()
+	server := h.server
+	h.server = nil
+	h.listener = nil
+	h.mu.Unlock()
+
+	if server == nil {
 		return nil
 	}
-	return h.server.Shutdown(ctx)
+
+	return server.Shutdown(ctx)
 }
 
 // Addr returns the actual address the server is listening on.