fix: remove unused isFailed variable in McpChatWeb progress endpoint

The variable was never read - status display uses reverseEngineeringFailed
(a derived check) and isCompleted/isRunning instead.
Resolves github-code-quality warning on PR #22.

Author: gkaleta

McpChatWeb/Program.cs

@@ -1853,7 +1853,6 @@ FROM chunk_metadata
 		// Determine stage statuses based on data
 		var isRunning = runStatus == "Running";
 		var isCompleted = runStatus == "Completed";
-		var isFailed = runStatus == "Failed";
 
 		// Check if this run used chunking (has chunk metadata)
 		var usedChunking = totalChunks > 0;