Use named regex capture groups for readability

Co-authored-by: stephentoub <2642209+stephentoub@users.noreply.github.com>

Author: Copilot

tests/ModelContextProtocol.AspNetCore.Tests/ClientConformanceTests.cs

@@ -141,10 +141,10 @@ private static bool HasOnlyWarnings(string output, string error)
         //   "Passed: 2/2, 0 failed, 1 warnings"
         // If there are 0 failures but warnings > 0, the test behavior is acceptable.
         var combined = output + error;
-        var match = Regex.Match(combined, @"(\d+) failed, (\d+) warnings");
+        var match = Regex.Match(combined, @"(?<failed>\d+) failed, (?<warnings>\d+) warnings");
         return match.Success
-            && match.Groups[1].Value == "0"
-            && int.TryParse(match.Groups[2].Value, out var warnings)
+            && match.Groups["failed"].Value == "0"
+            && int.TryParse(match.Groups["warnings"].Value, out var warnings)
             && warnings > 0;
     }
 }