[client] Adopt the three-value parseEmailFromIDToken in the device flow

The main merge brought in the device flow's email extraction from #7193,
which still used the two-value signature this branch replaced when account
matching was narrowed to the email claim. Git merged the files without a
textual conflict, so the branch stopped compiling.

Take the fromEmailClaim result and fill EmailClaim from it, the same way the
PKCE path does, so device-flow clients get the same account matching.

client/internal/auth/device_flow.go

@@ -308,10 +308,13 @@ func (d *DeviceAuthorizationFlow) WaitToken(ctx context.Context, info AuthFlowIn
 			// callers store to send back as the login_hint. Without it a client
 			// driven through the device flow — Android TV and tvOS — never binds
 			// an account to its profile and every later login goes out blind.
-			if email, err := parseEmailFromIDToken(tokenInfo.IDToken); err != nil {
+			if email, fromEmailClaim, err := parseEmailFromIDToken(tokenInfo.IDToken); err != nil {
 				log.Warnf("failed to parse email from ID token: %v", err)
 			} else {
 				tokenInfo.Email = email
+				if fromEmailClaim {
+					tokenInfo.EmailClaim = email
+				}
 			}
 
 			log.Infof("device flow: user authorization confirmed after %d polls in %s", polls, time.Since(start).Round(time.Second))