fix(worker): make external MCP filter params optional, surface tool errors

Nullable filter/patch params across the External/ MCP tool classes (ListTasks,
UpdateTask, AddSubtask, ReviewTask, SetMyDay, SetListConfig/SetTaskConfig,
CreateList/UpdateList) lacked C# default values, so the generated tool schema
marked them required — MCP clients omitting them (the common case) failed.
Gave every such parameter a default value.

Also registered a call-tool filter (ExternalMcpExceptionFilter) on the external
MCP host that translates InvalidOperationException/ArgumentException into
McpException, since the SDK's own catch-all discards ex.Message for any other
exception type and returns a generic "An error occurred invoking 'X'." string.

Added a reflection-based schema test sweeping every [McpServerToolType] class
to guard against reintroducing a required-but-nullable parameter.

src/ClaudeDo.Worker/Program.cs

@@ -282,6 +282,7 @@ if (cfg.ExternalMcpPort > 0)
     externalBuilder.Services.AddScoped<AttachmentMcpTools>();
     externalBuilder.Services.AddMcpServer()
         .WithHttpTransport()
+        .WithRequestFilters(f => f.AddCallToolFilter(ExternalMcpExceptionFilter.Wrap))
         .WithTools<ExternalMcpService>()
         .WithTools<BatchMcpTools>()
         .WithTools<ListMcpTools>()