fix(macos): harden presence decode

apps/macos/Tests/ClawdisIPCTests/InstancesStoreTests.swift

@@ -0,0 +1,36 @@
+import Testing
+@testable import Clawdis
+import ClawdisProtocol
+
+@Suite struct InstancesStoreTests {
+    @Test
+    @MainActor
+    func presenceEventPayloadDecodesViaJSONEncoder() {
+        // Build a payload that mirrors the gateway's presence event shape:
+        // { "presence": [ PresenceEntry ] }
+        let entry: [String: ClawdisProtocol.AnyCodable] = [
+            "host": .init("gw"),
+            "ip": .init("10.0.0.1"),
+            "version": .init("2.0.0"),
+            "mode": .init("gateway"),
+            "lastInputSeconds": .init(5),
+            "reason": .init("test"),
+            "text": .init("Gateway node"),
+            "ts": .init(1_730_000_000),
+        ]
+        let payloadMap: [String: ClawdisProtocol.AnyCodable] = [
+            "presence": .init([ClawdisProtocol.AnyCodable(entry)]),
+        ]
+        let payload = ClawdisProtocol.AnyCodable(payloadMap)
+
+        let store = InstancesStore(isPreview: true)
+        store.handlePresenceEventPayload(payload)
+
+        #expect(store.instances.count == 1)
+        let instance = store.instances.first
+        #expect(instance?.host == "gw")
+        #expect(instance?.ip == "10.0.0.1")
+        #expect(instance?.mode == "gateway")
+        #expect(instance?.reason == "test")
+    }
+}