Add missing node tracking for config-defined nodes

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

config.go

@@ -2,6 +2,7 @@ package tendrils
 
 import (
 	"encoding/json"
+	"net"
 	"os"
 
 	"gopkg.in/yaml.v3"
@@ -12,10 +13,54 @@ type Config struct {
 }
 
 type Location struct {
-	Name      string      `yaml:"name" json:"name"`
-	Direction string      `yaml:"direction,omitempty" json:"direction,omitempty"`
-	Nodes     []string    `yaml:"nodes,omitempty" json:"nodes,omitempty"`
-	Children  []*Location `yaml:"children,omitempty" json:"children,omitempty"`
+	Name      string       `yaml:"name" json:"name"`
+	Direction string       `yaml:"direction,omitempty" json:"direction,omitempty"`
+	Nodes     []*NodeRef   `yaml:"nodes,omitempty" json:"nodes,omitempty"`
+	Children  []*Location  `yaml:"children,omitempty" json:"children,omitempty"`
+}
+
+type NodeRef struct {
+	Name string `yaml:"name,omitempty" json:"name,omitempty"`
+	MAC  string `yaml:"mac,omitempty" json:"mac,omitempty"`
+	IP   string `yaml:"ip,omitempty" json:"ip,omitempty"`
+}
+
+func (r *NodeRef) DisplayName() string {
+	if r.Name != "" {
+		return r.Name
+	}
+	if r.MAC != "" {
+		return r.MAC
+	}
+	return r.IP
+}
+
+func (r *NodeRef) ParseMAC() net.HardwareAddr {
+	if r.MAC == "" {
+		return nil
+	}
+	mac, _ := net.ParseMAC(r.MAC)
+	return mac
+}
+
+func (r *NodeRef) ParseIP() net.IP {
+	if r.IP == "" {
+		return nil
+	}
+	return net.ParseIP(r.IP)
+}
+
+func (c *Config) AllNodeRefs() []*NodeRef {
+	var refs []*NodeRef
+	var collect func([]*Location)
+	collect = func(locs []*Location) {
+		for _, loc := range locs {
+			refs = append(refs, loc.Nodes...)
+			collect(loc.Children)
+		}
+	}
+	collect(c.Locations)
+	return refs
 }
 
 func LoadConfig(path string) (*Config, error) {