fix(update): surface API errors instead of silently returning null

- Log exception details (url/appKey/versionCode/userId) when checkUpdate fails
- Log warning + debug messages around awaitInitialization
- Helps diagnose SDK vs old private-server API incompatibilities

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

sdk-update/src/main/java/com/xuqm/sdk/update/UpdateSDK.kt

@@ -4,6 +4,7 @@ import android.content.Context
 import android.content.Intent
 import android.net.Uri
 import android.os.Build
+import android.util.Log
 import androidx.core.content.FileProvider
 import com.xuqm.sdk.XuqmSDK
 import com.xuqm.sdk.file.FileSDK
@@ -152,6 +153,7 @@ object UpdateSDK {
             packageInfo.versionCode
         }
         val userId = resolveUserId()
+        val url = ServiceEndpointRegistry.updateBaseUrl
         runCatching {
             api.checkUpdate(XuqmSDK.appKey, "ANDROID", versionCode, userId).data?.let { info ->
                 val normalized = info.copy(downloadUrl = normalizeDownloadUrl(info.downloadUrl) ?: info.downloadUrl)
@@ -171,16 +173,24 @@ object UpdateSDK {
                     afterIgnore
                 }
             }
+        }.onFailure { e ->
+            Log.e("UpdateSDK", "checkUpdate failed [url=$url appKey=${XuqmSDK.appKey} versionCode=$versionCode userId=$userId]: ${e.message}", e)
         }.getOrNull()
     }
 
     private suspend fun awaitInitialization() {
         if (XuqmSDK.isInitialized()) return
+        Log.w("UpdateSDK", "XuqmSDK not yet initialized, waiting up to 15s...")
         kotlinx.coroutines.withTimeoutOrNull(15_000L) {
             while (!XuqmSDK.isInitialized()) {
                 kotlinx.coroutines.delay(100)
             }
-        } ?: throw IllegalStateException("XuqmSDK not initialized. Check that config.xuqm is present and valid.")
+        } ?: run {
+            val msg = "XuqmSDK init timeout (15s). Check that config.xuqm is present and package name matches."
+            Log.e("UpdateSDK", msg)
+            throw IllegalStateException(msg)
+        }
+        Log.d("UpdateSDK", "XuqmSDK initialized, proceeding with update check")
     }
 
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