In plugins/fs/guest-js/index.ts, the size function only sent `path`
although the Rust command accepts `options.baseDir` and the JSDoc example
passed `{ baseDir: BaseDirectory.AppData }` (a TS error, silently dropped
at runtime, so the relative path was rejected).
Adds an optional `options?: SizeOptions` parameter (new exported type).
api-iife.js regenerated. The e2e spec now measures a file and a directory
relative to AppData instead of working around the missing option.