fix(sdk): improve SNS login binding and account handling

- Remove premature null check in LoginBySns to allow login flow
- Add debug logging for SNS login failures
- Handle code==-1 case when binding accounts with same userId

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

sdk-intergration/Packages/tysdk/Runtime/TYSdkFacade.cs

@@ -221,8 +221,7 @@ namespace tysdk
         
         public async Task<LoginInfo> LoginBySns()
         {
-            var accountInfo = AccountInfo.GetSavedAccoutInfo();
+            Debug.Log("[TYSdkFacade] LoginBySns");
-            if (accountInfo == null) return new LoginInfo();
 
             var task = TYSDKCallbackManager.Instance.RegisterCallback<LoginInfo>(TimeSpan.FromSeconds(30));
 
@@ -240,6 +239,10 @@ namespace tysdk
                     _accountInfo.AddLinkedAccount(accountType);
                     _accountInfo.Save();
                 }
+                else
+                {
+                    Debug.Log($"[TYSdkFacade] LoginBySns failed  snsType: {snsType}");
+                }
                 return loginInfo;
             }
             catch (Exception e)
@@ -331,6 +334,12 @@ namespace tysdk
                         _accountInfo.Save();
                     }
                 }
+                else if (result.code == -1 && _accountInfo.userId == result.userId)
+                {
+                    _accountInfo.channel = accoutType;
+                    _accountInfo.AddLinkedAccount(accoutType);
+                    _accountInfo.Save();
+                }
                 return result;
             }
             catch (Exception e)