Reuse McpToolOutput in McpHandler (#14229)

We already have a type to represent the MCP tool output, reuse it
instead of the custom McpHandlerOutput

codex-rs/core/src/tools/parallel.rs

@@ -124,7 +124,9 @@ impl ToolCallRuntime {
             },
             ToolPayload::Mcp { .. } => ResponseInputItem::McpToolCallOutput {
                 call_id: call.call_id.clone(),
-                result: Err(Self::abort_message(call, secs)),
+                output: codex_protocol::models::McpToolOutput::from_error_text(
+                    Self::abort_message(call, secs),
+                ),
             },
             _ => ResponseInputItem::FunctionCallOutput {
                 call_id: call.call_id.clone(),