test: extend SessionBatchViewBuilderTests with edge cases

- Empty sessions
- Confirmed status
- Null MaxPlayers

Issue: #33

tests/GmRelay.Bot.Tests/Rendering/SessionBatchViewBuilderTests.cs

@@ -110,4 +110,38 @@ public sealed class SessionBatchViewBuilderTests
         Assert.Equal("Alice", player.DisplayName);
         Assert.Equal("alice", player.TelegramUsername);
     }
+
+    [Fact]
+    public void Build_ShouldHandleEmptySessions()
+    {
+        var result = SessionBatchViewBuilder.Build("Empty", [], []);
+        Assert.Equal("Empty", result.Title);
+        Assert.Empty(result.Sessions);
+    }
+
+    [Fact]
+    public void Build_ShouldHandleConfirmedStatus()
+    {
+        var sessionId = Guid.NewGuid();
+        var sessions = new[] { new SessionBatchDto(sessionId, DateTime.UtcNow, SessionStatus.Confirmed, 4, "https://example.com/game") };
+        var participants = Array.Empty<ParticipantBatchDto>();
+
+        var result = SessionBatchViewBuilder.Build("Test", sessions, participants);
+
+        Assert.Equal(SessionStatus.Confirmed, result.Sessions[0].Status);
+        Assert.Equal(2, result.Sessions[0].AvailableActions.Count);
+    }
+
+    [Fact]
+    public void Build_ShouldHandleNullMaxPlayers()
+    {
+        var sessionId = Guid.NewGuid();
+        var sessions = new[] { new SessionBatchDto(sessionId, DateTime.UtcNow, SessionStatus.Planned, null, "https://example.com/game") };
+        var participants = Array.Empty<ParticipantBatchDto>();
+
+        var result = SessionBatchViewBuilder.Build("Test", sessions, participants);
+
+        Assert.Null(result.Sessions[0].MaxPlayers);
+        Assert.Equal(0, result.Sessions[0].ActivePlayerCount);
+    }
 }