refactor(gateway): unify v3 auth payload builders and vectors

apps/android/app/src/test/java/ai/openclaw/android/gateway/DeviceAuthPayloadTest.kt

@@ -0,0 +1,35 @@
+package ai.openclaw.android.gateway
+
+import org.junit.Assert.assertEquals
+import org.junit.Test
+
+class DeviceAuthPayloadTest {
+  @Test
+  fun buildV3_matchesCanonicalVector() {
+    val payload =
+      DeviceAuthPayload.buildV3(
+        deviceId = "dev-1",
+        clientId = "openclaw-macos",
+        clientMode = "ui",
+        role = "operator",
+        scopes = listOf("operator.admin", "operator.read"),
+        signedAtMs = 1_700_000_000_000,
+        token = "tok-123",
+        nonce = "nonce-abc",
+        platform = "  IOS  ",
+        deviceFamily = "  iPhone  ",
+      )
+
+    assertEquals(
+      "v3|dev-1|openclaw-macos|ui|operator|operator.admin,operator.read|1700000000000|tok-123|nonce-abc|ios|iphone",
+      payload,
+    )
+  }
+
+  @Test
+  fun normalizeMetadataField_asciiOnlyLowercase() {
+    assertEquals("İos", DeviceAuthPayload.normalizeMetadataField("  İOS  "))
+    assertEquals("mac", DeviceAuthPayload.normalizeMetadataField("  MAC  "))
+    assertEquals("", DeviceAuthPayload.normalizeMetadataField(null))
+  }
+}