fix(claude-do): snake_case Serilog tokens + no Warning-log on cancelled hub calls

Message-template tokens must be snake_case (repo rule) -- fixes 4 PascalCase
tokens introduced in 57dd6766. TryInvokeAsync's swallowing catch also no
longer logs a Warning for OperationCanceledException, which is routine
(e.g. worker shutdown/reconnect), not a failure worth a trace.

ClaudeDo-Task: d2ae3831-733f-4d40-93d7-70c93da11590

src/ClaudeDo.Worker/Hub/HubExceptionLoggingFilter.cs

@@ -20,7 +20,7 @@ public sealed class HubExceptionLoggingFilter(ILogger<HubExceptionLoggingFilter>
         }
         catch (Exception ex)
         {
-            logger.LogWarning(ex, "Hub method {Method} failed", invocationContext.HubMethodName);
+            logger.LogWarning(ex, "Hub method {method_name} failed", invocationContext.HubMethodName);
             throw;
         }
     }