fix: handle long-running executor prompts

app/src/core/contracts.ts

@@ -7,6 +7,19 @@ export const generatedLabel = "agent:generated";
 export const blockedLabel = "agent:blocked";
 export const planReadyLabel = "agent:plan-ready";
 
+export function log(
+    level: string,
+    message: string,
+    fields: Record<string, unknown>,
+): string {
+    return JSON.stringify({
+        level,
+        message,
+        ...fields,
+        time: new Date().toISOString(),
+    });
+}
+
 export type Mode = "plan" | "implement";
 
 export interface PlanData {