leave a breadcrumb comment about batchWindow zero (#31508)

packages/core/src/observability/logging.ts

@@ -47,6 +47,7 @@ function format(input: unknown) {
 }
 
 export function fileLogger(file = path.join(Global.Path.log, "opencode.log"), id: string = runID) {
+  // Do not set batchWindow to 0; it causes high idle CPU usage.
   return Logger.toFile(formatter(id), file, { flag: "a" })
 }