feat(macos): clarify local gateway choice

apps/macos/Tests/ClawdisIPCTests/GatewayDiscoveryModelTests.swift

@@ -0,0 +1,48 @@
+import Testing
+@testable import Clawdis
+
+@Suite struct GatewayDiscoveryModelTests {
+    @Test func localGatewayMatchesLanHost() {
+        let local = GatewayDiscoveryModel.LocalIdentity(
+            hostTokens: ["studio"],
+            displayTokens: [])
+        #expect(GatewayDiscoveryModel.isLocalGateway(
+            lanHost: "studio.local",
+            tailnetDns: nil,
+            displayName: nil,
+            local: local))
+    }
+
+    @Test func localGatewayMatchesTailnetDns() {
+        let local = GatewayDiscoveryModel.LocalIdentity(
+            hostTokens: ["studio"],
+            displayTokens: [])
+        #expect(GatewayDiscoveryModel.isLocalGateway(
+            lanHost: nil,
+            tailnetDns: "studio.tailnet.example",
+            displayName: nil,
+            local: local))
+    }
+
+    @Test func localGatewayMatchesDisplayName() {
+        let local = GatewayDiscoveryModel.LocalIdentity(
+            hostTokens: [],
+            displayTokens: ["peter's mac studio"])
+        #expect(GatewayDiscoveryModel.isLocalGateway(
+            lanHost: nil,
+            tailnetDns: nil,
+            displayName: "Peter's Mac Studio (Clawdis)",
+            local: local))
+    }
+
+    @Test func remoteGatewayDoesNotMatch() {
+        let local = GatewayDiscoveryModel.LocalIdentity(
+            hostTokens: ["studio"],
+            displayTokens: ["peter's mac studio"])
+        #expect(!GatewayDiscoveryModel.isLocalGateway(
+            lanHost: "other.local",
+            tailnetDns: "other.tailnet.example",
+            displayName: "Other Mac",
+            local: local))
+    }
+}