Split the 316-line vendors index into VendorToolbar, VendorGrid,
VendorList, and PerPageSelector under components/vendors/. Page now
owns only search-param state and query orchestration.
Replace generic Error throws in lib/directus.ts with a DirectusError
class carrying status, statusText, collection, url, and parsed body.
Surface useLocalStorage read/write failures via console.warn instead
of swallowing them.
