fix(FN-1952): restore pi auth and extension loading

packages/dashboard/src/milestone-slice-interview.ts

@@ -101,7 +101,11 @@ async function initEngine() {
   }
 }
 
-const engineReady = initEngine();
+let engineReady: Promise<void> | undefined;
+function ensureEngineReady() {
+  engineReady ??= initEngine();
+  return engineReady;
+}
 
 // ── Constants ───────────────────────────────────────────────────────────────
 
@@ -492,6 +496,7 @@ function cleanupExpiredSessions(): void {
 }
 
 const cleanupInterval = setInterval(cleanupExpiredSessions, CLEANUP_INTERVAL_MS);
+cleanupInterval.unref?.();
 process.on("beforeExit", () => clearInterval(cleanupInterval));
 
 // ── Stream Manager ──────────────────────────────────────────────────────────
@@ -671,7 +676,7 @@ async function createTargetInterviewAgent(
   session: TargetInterviewSession,
   rootDir: string,
 ): Promise<AgentResult> {
-  await engineReady;
+  await ensureEngineReady();
 
   return createKbAgent({
     cwd: rootDir,