feat: vendor permission system source

pi-permission-system/src/async-cache.ts

@@ -0,0 +1,21 @@
+/**
+ * Memoize an async factory, but drop a rejected result so the next call
+ * retries.
+ *
+ * On success the resolved promise is cached and shared across all callers (the
+ * factory runs once). On failure the cache is cleared before the rejection is
+ * re-thrown, so a transient init failure does not poison the memo for the
+ * process lifetime — the next call re-invokes the factory.
+ */
+export function memoizeAsyncWithRetry<T>(
+  factory: () => Promise<T>,
+): () => Promise<T> {
+  let cached: Promise<T> | null = null;
+  return () => {
+    cached ??= factory().catch((error: unknown) => {
+      cached = null; // poisoned result cleared → next call re-attempts
+      throw error;
+    });
+    return cached;
+  };
+}