switch id model to this

the wakey-core id model is (seemingly) ephemeral

src/service/inventory.rs

@@ -103,7 +103,7 @@ const fn presence_rank(presence: Presence) -> u8 {
 mod tests {
     use super::*;
     use std::net::{IpAddr, Ipv4Addr};
-    use wakey_core::{DhcpLease, InventoryQueryBuilder, NeighborState};
+    use wakey_core::{DeviceId, DhcpLease, InventoryQueryBuilder, NeighborState};
 
     fn sample_neighbors() -> Vec<NeighborEntry> {
         vec![NeighborEntry {
@@ -154,4 +154,25 @@ mod tests {
         let out = merge_devices(sample_neighbors(), sample_leases(), &query);
         assert_eq!(out.len(), 1);
     }
+
+    #[test]
+    fn merge_devices_uses_ip_observed_id_when_mac_is_absent() {
+        let query = InventoryQueryBuilder::new().build();
+        let out = merge_devices(
+            vec![NeighborEntry {
+                ip: IpAddr::V4(Ipv4Addr::new(192, 168, 1, 20)),
+                dev: Some("br-lan".to_string()),
+                mac: None,
+                state: NeighborState::Stale,
+            }],
+            Vec::new(),
+            &query,
+        );
+
+        assert_eq!(out.len(), 1);
+        assert_eq!(
+            out[0].id,
+            Some(DeviceId::Ip(IpAddr::V4(Ipv4Addr::new(192, 168, 1, 20))))
+        );
+    }
 }

wakey-core/src/model/device.rs

@@ -1,5 +1,5 @@
 use macaddr::MacAddr;
-use serde::Serialize;
+use serde::{Deserialize, Serialize};
 use serde_with::skip_serializing_none;
 use std::net::IpAddr;
 
@@ -32,11 +32,16 @@ impl From<NeighborState> for Presence {
     }
 }
 
-/// MAC-first identifier for a device aggregate.
-#[derive(Debug, PartialEq, Eq, Clone, Hash, Serialize)]
-pub struct DeviceId {
+/// Observed identifier for a discovered device aggregate.
+///
+/// This is not a durable, user-approved identity. The control plane may attach
+/// many observed identifiers to one saved device.
+#[derive(Debug, PartialEq, Eq, Clone, Hash, Serialize, Deserialize)]
+#[serde(tag = "kind", content = "value", rename_all = "snake_case")]
+pub enum DeviceId {
     #[serde(with = "mac")]
-    pub mac: MacAddr,
+    Mac(MacAddr),
+    Ip(IpAddr),
 }
 
 /// Merged view of one discovered network identity.
@@ -91,10 +96,16 @@ impl Device {
         }
 
         let macs: Vec<MacAddr> = macs.into_iter().collect();
+        let ips: Vec<IpAddr> = ips.into_iter().collect();
+        let id = macs
+            .first()
+            .copied()
+            .map(DeviceId::Mac)
+            .or_else(|| ips.first().copied().map(DeviceId::Ip));
         Self {
-            id: macs.first().copied().map(|mac| DeviceId { mac }),
+            id,
             names: names.into_iter().map(|n| n.to_owned()).collect(),
-            ips: ips.into_iter().collect(),
+            ips,
             macs,
             interfaces: interfaces.into_iter().map(|d| d.to_owned()).collect(),
             neighbors,