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

apps/android/app/src/main/java/ai/openclaw/android/gateway/DeviceAuthPayload.kt

@@ -0,0 +1,52 @@
+package ai.openclaw.android.gateway
+
+internal object DeviceAuthPayload {
+  fun buildV3(
+    deviceId: String,
+    clientId: String,
+    clientMode: String,
+    role: String,
+    scopes: List<String>,
+    signedAtMs: Long,
+    token: String?,
+    nonce: String,
+    platform: String?,
+    deviceFamily: String?,
+  ): String {
+    val scopeString = scopes.joinToString(",")
+    val authToken = token.orEmpty()
+    val platformNorm = normalizeMetadataField(platform)
+    val deviceFamilyNorm = normalizeMetadataField(deviceFamily)
+    return listOf(
+      "v3",
+      deviceId,
+      clientId,
+      clientMode,
+      role,
+      scopeString,
+      signedAtMs.toString(),
+      authToken,
+      nonce,
+      platformNorm,
+      deviceFamilyNorm,
+    ).joinToString("|")
+  }
+
+  internal fun normalizeMetadataField(value: String?): String {
+    val trimmed = value?.trim().orEmpty()
+    if (trimmed.isEmpty()) {
+      return ""
+    }
+    // Keep cross-runtime normalization deterministic (TS/Swift/Kotlin):
+    // lowercase ASCII A-Z only for auth payload metadata fields.
+    val out = StringBuilder(trimmed.length)
+    for (ch in trimmed) {
+      if (ch in 'A'..'Z') {
+        out.append((ch.code + 32).toChar())
+      } else {
+        out.append(ch)
+      }
+    }
+    return out.toString()
+  }
+}

apps/android/app/src/main/java/ai/openclaw/android/gateway/GatewaySession.kt

@@ -372,7 +372,7 @@ class GatewaySession(
 
       val signedAtMs = System.currentTimeMillis()
       val payload =
-        buildDeviceAuthPayloadV3(
+        DeviceAuthPayload.buildV3(
           deviceId = identity.deviceId,
           clientId = client.id,
           clientMode = client.mode,
@@ -584,42 +584,6 @@ class GatewaySession(
     }
   }
 
-  private fun buildDeviceAuthPayloadV3(
-    deviceId: String,
-    clientId: String,
-    clientMode: String,
-    role: String,
-    scopes: List<String>,
-    signedAtMs: Long,
-    token: String?,
-    nonce: String,
-    platform: String?,
-    deviceFamily: String?,
-  ): String {
-    val scopeString = scopes.joinToString(",")
-    val authToken = token.orEmpty()
-    val platformNorm = normalizeDeviceMetadataField(platform)
-    val deviceFamilyNorm = normalizeDeviceMetadataField(deviceFamily)
-    val parts =
-      mutableListOf(
-        "v3",
-        deviceId,
-        clientId,
-        clientMode,
-        role,
-        scopeString,
-        signedAtMs.toString(),
-        authToken,
-        nonce,
-        platformNorm,
-        deviceFamilyNorm,
-      )
-    return parts.joinToString("|")
-  }
-
-  private fun normalizeDeviceMetadataField(value: String?): String =
-    value?.trim()?.lowercase(Locale.ROOT).orEmpty()
-
   private fun normalizeCanvasHostUrl(
     raw: String?,
     endpoint: GatewayEndpoint,