Routing Reliability, Base Paths, and Cancellable Loaders

Contract change type: additive

Added

• Added RouterOptions.basePath for deploying an app under a URL prefix (e.g. /portal) —
  stripped before route matching and re-applied by navigate(), replace(), href(), and
  link interception.
• Route.loader now receives an AbortSignal, aborted when a navigation is superseded by
  another before the loader resolves (or on router.destroy()), so expensive in-flight work
  (e.g. fetch()) can be cancelled. Existing loaders that ignore the argument are unaffected.

Changed

• Updated development tooling to ESLint 10.10 and Vitest 5.0.

Fixed

• Handle malformed path encoding through onError and the configured error route instead of
  producing an unhandled rejection.
• Clean up rendered parent pages when a required nested routing outlet is missing.
• Preserve the full previous URL, including query strings and fragments, when a navigation
  guard cancels navigation in history or hash mode.
• Invoke onError for unmatched routes even when no error route is configured.