A plugin-authored, structured error — throw this (instead of a plain throw new Error(...)) to report {error_code, data} through an exception rather than a return {error}. error_code doubles as an i18n lookup key (see crates/lanrurugi-plugin/dispatcher/plugin-sdk.ts's PluginError for the full field-meaning docs — this class's fields mirror that interface exactly). The dispatcher's own catch (dispatcher.ts's handleRequest) uses real instanceof against this exact class to extract error_code/data for the Rust host.

The real class lives in plugin-sdk.ts and is exposed here only as a global (globalThis.PluginErrorException = PluginErrorException in dispatcher.ts) so every plugin file can use it with zero import of its own — a plugin file's static import specifier can't reach plugin-sdk.ts at all, since plugins_dir and plugin-sdk.ts's own directory (temp_dir) have no fixed relative path between them (both are independent runtime CLI args). declare class here (rather than declare var ...: PluginError) is what lets a plugin file both throw new PluginErrorException(...) (construct) and catch it with instanceof (matches the value dispatcher.ts actually assigns, a real ES class, not just its instance shape).