feat(data): persist max_turns in list and task repositories

Add MaxTurns to ListRepository.SetConfigAsync upsert branch and
TaskRepository.UpdateAgentSettingsAsync; fix positional CancellationToken
call in ConfigMcpTools. Covered by MaxTurnsRoundTripTests (2 tests).

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

src/ClaudeDo.Data/Repositories/ListRepository.cs

@@ -65,6 +65,7 @@ public sealed class ListRepository
             existing.Model = config.Model;
             existing.SystemPrompt = config.SystemPrompt;
             existing.AgentPath = config.AgentPath;
+            existing.MaxTurns = config.MaxTurns;
         }
         await _context.SaveChangesAsync(ct);
     }