feat: Enable /setup-github to always run, and error appropriately (#5653)

Co-authored-by: Jacob Richman <jacob314@gmail.com>

packages/cli/src/ui/commands/setupGithubCommand.test.ts

@@ -61,6 +61,8 @@ describe('setupGithubCommand', () => {
     vi.mocked(child_process.execSync).mockReturnValue('');
     expect(() => {
       setupGithubCommand.action?.({} as CommandContext, '');
-    }).toThrow('Unable to determine the Git root directory.');
+    }).toThrow(
+      'Unable to determine the GitHub repository. /setup-github must be run from a git repository.',
+    );
   });
 });