Merge all changes

src/Notify/__Tests/StellaOps.Notify.Connectors.Email.Tests/ErrorHandling/EmailConnectorErrorTests.cs

@@ -605,7 +605,7 @@ internal sealed class EmailConnector
             result.FailedRecipients = ex.InnerExceptions
                 .OfType<SmtpFailedRecipientException>()
                 .Select(e => e.FailedRecipient)
-                .ToList();
+                .Where(r => r is not null).Cast<string>().ToList();
             return result;
         }
         catch (SmtpFailedRecipientException ex)
@@ -616,7 +616,7 @@ internal sealed class EmailConnector
             // Classify recipient failure
             (result.ErrorCode, result.ShouldRetry) = ex.StatusCode switch
             {
-                SmtpStatusCode.MailboxUnavailable when ex.FailedRecipient.Contains('@') == false
+                SmtpStatusCode.MailboxUnavailable when ex.FailedRecipient?.Contains('@') == false
                     => ("INVALID_RECIPIENT", false),
                 SmtpStatusCode.MailboxUnavailable => ("MAILBOX_NOT_FOUND", false),
                 SmtpStatusCode.ExceededStorageAllocation => ("MAILBOX_FULL", true),

src/Notify/__Tests/StellaOps.Notify.Connectors.Slack.Tests/SlackChannelTestProviderTests.cs

@@ -47,6 +47,7 @@ public sealed class SlackChannelTestProviderTests
 
         Assert.Equal("slack", result.Preview.ChannelType.ToString().ToLowerInvariant());
         Assert.Equal(channel.Config.Target, result.Preview.Target);
+        Assert.NotNull(result.Metadata);
         Assert.Equal("chat:write,chat:write.public", result.Metadata["slack.scopes.required"]);
         Assert.Equal("stellaops-sec", result.Metadata["slack.config.workspace"]);
 
@@ -89,6 +90,7 @@ public sealed class SlackChannelTestProviderTests
 
         var result = await provider.BuildPreviewAsync(context, CancellationToken.None);
 
+        Assert.NotNull(result.Metadata);
         Assert.Equal("***", result.Metadata["slack.config.SigningSecret"]);
         Assert.DoesNotContain("xoxs-000000000000-super", result.Metadata["slack.config.apiToken"]);
         Assert.Equal("https://hooks.slack.com/services/T000/B000/AAA", result.Metadata["slack.config.endpoint"]);