Add type-safe custom data for `notFound`

notFound({ data }) currently accepts any, while notFoundComponent receives data as unknown. This forces consumers to add their own type guards or casts.

Add a shared type-safe way to configure custom not-found data. The solution should:

• Work through the shared router-core NotFoundError type.
• Type notFound, routeApi.notFound, and NotFoundRouteProps.data consistently.
• Cover React, Solid, and Vue bindings.
• Decide whether the type is global through Register or configurable per route.
• Preserve existing behavior for applications that do not configure a custom type.
• Add type tests for returned and thrown not-found errors.
• Update the notFound reference documentation with the supported augmentation pattern.
• Avoid runtime or bundle-size changes.

Related: #3112 and discussion #3113.

Read the shared router-core NotFoundError type first, then trace notFound, routeApi.notFound, and NotFoundRouteProps.data across the React, Solid, and Vue bindings. Review the related pull request and discussion for the global-versus-per-route decision. Add the requested type tests for returned and thrown errors, update the notFound reference documentation with the supported augmentation pattern, and verify unchanged behavior without custom configuration.