The constructor `NewStateRootNotFoundError` incorrectly returned
`StateNotFoundError`. This prevented handlers that rely on
errors.As(err, *lookup.StateRootNotFoundError) from matching and mapping
the error to HTTP 404. The function now returns
StateRootNotFoundError and constructs that type, restoring the intended
behavior for “state root not found” cases.
---------
Co-authored-by: Radosław Kapka <rkapka@wp.pl>
