Authorization challenges show connector display name

Patch Changes

• 2f8d81f: Surface the connector's human-readable name through authorization challenges. startAuthorization now exposes the optional connector object returned by POST /v1/connect/authorize/:connector (matching the connector object on the token response), and the Eve connect() adapter stamps the service display name (connector.serviceName, eg. "Salesforce", falling back to the connector's own connector.name for unknown services) onto the ConnectionAuthorizationChallenge as displayName so channels can render "Sign in with Salesforce" instead of a title-cased file name. Connection authors can override the server-reported name via the new displayName option on connect(). No behavior change until the Vercel API starts returning connector.