Better Auth Steam Plugin

Steam OpenID 2.0 plugin for Better Auth, providing Steam login via two endpoints: GET /api/auth/steam/login and GET /api/auth/steam/callback. It adds a nullable unique steamId field on the user model and requires better-auth >= 1.4.0 and zod >= 4 as peer dependencies. Version 0.1.1 ships TypeScript types. Key differentiators: full Steam OpenID assertion validation using check_authentication, synthetic email generation for users without email, and customizable profile mapping.