fix(desktop): preserve workspace execution error categories

Keep workspace runner errorCategory metadata on propagated execution failures so desktop diagnostics can distinguish failure types.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

apps/desktop/src/main/services/project-workspace-executor.ts

@@ -27,6 +27,7 @@ interface RunnerEvent {
   label?: string;
   detail?: string;
   message?: string;
+  errorCategory?: string;
   content?: string;
   textDelta?: string;
   fullText?: string;
@@ -70,6 +71,14 @@ function toErrorMessage(error: unknown): string {
   return String(error);
 }
 
+function buildWorkspaceExecutionError(message: string, errorCategory?: string): Error & { errorCategory?: string } {
+  const error = new Error(message) as Error & { errorCategory?: string };
+  if (errorCategory) {
+    error.errorCategory = errorCategory;
+  }
+  return error;
+}
+
 async function pathExists(targetPath: string): Promise<boolean> {
   try {
     await stat(targetPath);
@@ -320,12 +329,12 @@ export class ProjectWorkspaceExecutorService {
         ], spawnOptions);
       }
 
-      const finishWithError = (message: string) => {
+      const finishWithError = (message: string, errorCategory?: string) => {
         if (settled) {
           return;
         }
         settled = true;
-        reject(new Error(message));
+        reject(buildWorkspaceExecutionError(message, errorCategory));
       };
 
       child.stdout.setEncoding("utf8");
@@ -381,7 +390,10 @@ export class ProjectWorkspaceExecutorService {
           }
 
           if (event.type === "error") {
-            finishWithError(event.message?.trim() || "Project workspace execution failed.");
+            finishWithError(
+              event.message?.trim() || "Project workspace execution failed.",
+              typeof event.errorCategory === "string" ? event.errorCategory.trim() || undefined : undefined
+            );
             return;
           }
         }