India has dealt a potentially fatal blow to the World Trade Organization’s hopes of modernizing the rules of global commerce and remaining the central forum for multilateral trade deals. In the longer run, it means trade liberalization may advance — if at all — among narrower groups of countries, denying dissenters a chance to block progress. While the unwieldy 160-member, Geneva-based WTO will survive as a body for enforcing existing multilateral agreements, smaller clubs of like-minded nations are trying to move ahead faster to update the trade rules among themselves.