get_logger($name, $category)/get_plugin_logger()'s return shape. The legacy versions write
to a real rotating log file on disk (LANraragi::Utils::Logging); most converted plugins don't
get filesystem write access under declared_permissions (constitution Principle IV), so this
logs to stderr instead — safe because dispatcher.ts's own stdout is reserved for its
newline-delimited JSON protocol (see writeLine below) and stderr doesn't share that stream.
Usage
import { type LegacyLogger } from "plugins/legacy-globals.d.ts";