Remove redundant DisposeAsync call and simplify catch blocks in CreateAsync

ConnectAsync already calls DisposeAsync (which awaits Completion) before
re-throwing, so the session is already disposed and Completion is resolved
by the time CreateAsync's catch block runs.

Agent-Logs-Url: https://github.com/modelcontextprotocol/csharp-sdk/sessions/dc4efc81-4b40-45c3-a743-59ade1c1c6df

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

Author: Copilot

src/ModelContextProtocol.Core/Client/McpClient.Methods.cs

@@ -52,15 +52,14 @@ public static async Task<McpClient> CreateAsync(
         {
             await clientSession.ConnectAsync(cancellationToken).ConfigureAwait(false);
         }
-        catch (Exception ex) when (ex is not TransportClosedException)
+        catch (Exception ex) when (ex is not OperationCanceledException and not TransportClosedException)
         {
-            // ConnectAsync already disposed the session. Call DisposeAsync again (no-op)
-            // to ensure cleanup, then check if the transport provided structured completion
-            // details indicating why the transport closed.
+            // ConnectAsync already disposed the session (which includes awaiting Completion).
+            // Check if the transport provided structured completion details indicating
+            // why the transport closed that aren't already in the original exception chain.
             ClientCompletionDetails? completionDetails = null;
             try
             {
-                await clientSession.DisposeAsync().ConfigureAwait(false);
                 completionDetails = await clientSession.Completion.ConfigureAwait(false);
             }
             catch { } // allow the original exception to propagate if completion is unavailable
@@ -79,19 +78,6 @@ public static async Task<McpClient> CreateAsync(
 
             throw;
         }
-        catch
-        {
-            // The exception is already a TransportClosedException (e.g., from
-            // ProcessMessagesCoreAsync propagating channel completion details).
-            // Just ensure cleanup and re-throw.
-            try
-            {
-                await clientSession.DisposeAsync().ConfigureAwait(false);
-            }
-            catch { }
-
-            throw;
-        }
 
         return clientSession;
     }