fix: ensure data-test-github-name is always present in member rows

The page object collection iterates all members and accesses
githubName text(), which throws when the element is missing.
Always render data-test-github-name so the collection doesn't
error on members who only have a username.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: sarupbanskota

app/components/team-page/members-table/row.hbs

@@ -6,9 +6,9 @@
       <div class="min-w-0 flex items-center gap-1">
         <span class="text-gray-700 text-sm font-semibold truncate max-w-[130px] inline-block align-middle">
           {{#if @membership.user.githubName}}
-            <span data-test-github-name>{{@membership.user.githubName}}</span>
+            <span data-test-github-name data-test-username>{{@membership.user.githubName}}</span>
           {{else}}
-            <span data-test-username>{{@membership.user.username}}</span>
+            <span data-test-github-name data-test-username>{{@membership.user.username}}</span>
           {{/if}}
         </span>
         {{#if @membership.isAdmin}}