Apply suggestions from code review

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: bgavrilMS

src/client/Microsoft.Identity.Client/Instance/Discovery/InstanceDiscoveryManager.cs

@@ -205,7 +205,7 @@ private async Task<InstanceDiscoveryMetadataEntry> FetchNetworkMetadataOrFallbac
             catch (Exception e) 
             { 
                 requestContext.Logger.Warning(
-                    $"[Instance Discovery] Instance Discovery failed. MSAL will continue without instance metadata. \n\r" +
+                    $"[Instance Discovery] Instance Discovery failed. MSAL will continue without instance metadata. {Environment.NewLine}" +
                     $" Exception: {e} ");
 
                 var fallbackEntry =

src/client/Microsoft.Identity.Client/Instance/Discovery/NetworkMetadataProvider.cs

@@ -97,21 +97,18 @@ private async Task<InstanceDiscoveryResponse> SendInstanceDiscoveryRequestAsync(
             using var linkedCts = CancellationTokenSource.CreateLinkedTokenSource(
                 requestContext.UserCancellationToken, timeoutCts.Token);
 
-            CancellationToken originalToken = requestContext.UserCancellationToken;
-            requestContext.UserCancellationToken = linkedCts.Token;
-
-            try
+            // Use a dedicated RequestContext for instance discovery so that we don't mutate
+            // the caller's UserCancellationToken when injecting the internal timeout.
+            var discoveryRequestContext = new RequestContext(requestContext)
             {
-                InstanceDiscoveryResponse discoveryResponse = await client
-                    .DiscoverAadInstanceAsync(instanceDiscoveryEndpoint, requestContext)
-                    .ConfigureAwait(false);
+                UserCancellationToken = linkedCts.Token
+            };
 
-                return discoveryResponse;
-            }
-            finally
-            {
-                requestContext.UserCancellationToken = originalToken;
-            }
+            InstanceDiscoveryResponse discoveryResponse = await client
+                .DiscoverAadInstanceAsync(instanceDiscoveryEndpoint, discoveryRequestContext)
+                .ConfigureAwait(false);
+
+            return discoveryResponse;
         }
 
         private Uri ComputeHttpEndpoint(Uri authority, RequestContext requestContext)

src/client/Microsoft.Identity.Client/Internal/RequestContext.cs

@@ -27,7 +27,7 @@ internal class RequestContext
         /// </summary>
         public ApiEvent ApiEvent { get; set; }
 
-        public CancellationToken UserCancellationToken { get; set; }
+        public CancellationToken UserCancellationToken { get; }
 
         public X509Certificate2 MtlsCertificate { get; }