feat: surface workflow diagnostics

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

src/main/AryxAppService.ts

@@ -2504,6 +2504,21 @@ export class AryxAppService extends EventEmitter<AppServiceEvents> {
           agentName: event.agentName,
         });
         return;
+      case 'workflow-diagnostic':
+        this.emitSessionEvent({
+          sessionId,
+          kind: 'workflow-diagnostic',
+          occurredAt,
+          agentId: event.agentId,
+          agentName: event.agentName,
+          diagnosticSeverity: event.severity,
+          diagnosticKind: event.diagnosticKind,
+          diagnosticMessage: event.message,
+          executorId: event.executorId,
+          subworkflowId: event.subworkflowId,
+          exceptionType: event.exceptionType,
+        });
+        return;
       case 'assistant-usage':
         this.emitSessionEvent({
           sessionId,

src/main/sidecar/runTurnPending.ts

@@ -15,6 +15,7 @@ import type {
   AssistantUsageEvent,
   AssistantIntentEvent,
   ReasoningDeltaEvent,
+  WorkflowDiagnosticEvent,
 } from '@shared/contracts/sidecar';
 import type { ChatMessageRecord } from '@shared/domain/session';
 
@@ -27,7 +28,8 @@ export type TurnScopedEvent =
   | PendingMessagesModifiedEvent
   | AssistantUsageEvent
   | AssistantIntentEvent
-  | ReasoningDeltaEvent;
+  | ReasoningDeltaEvent
+  | WorkflowDiagnosticEvent;
 
 export interface RunTurnPendingCommand {
   kind: 'run-turn';

src/main/sidecar/sidecarProcess.ts

@@ -454,6 +454,7 @@ export class SidecarClient {
       case 'session-usage':
       case 'session-compaction':
       case 'pending-messages-modified':
+      case 'workflow-diagnostic':
       case 'assistant-usage':
       case 'assistant-intent':
       case 'reasoning-delta':