refactor(chat): tighten media cache boundaries

src/lib/browser/persistent_storage.ts

@@ -0,0 +1,20 @@
+"use client";
+
+import { Logger } from "@/utils";
+
+const log = new Logger("LibBrowserPersistentStorage");
+let storagePersistenceRequested = false;
+
+export async function requestBrowserPersistentStorageOnce(): Promise<void> {
+  if (storagePersistenceRequested) return;
+  storagePersistenceRequested = true;
+  if (typeof navigator === "undefined") return;
+  if (!navigator.storage?.persist) return;
+
+  try {
+    const persisted = await navigator.storage.persist();
+    log.debug("[persistent-storage] requested", { persisted });
+  } catch (error) {
+    log.debug("[persistent-storage] request skipped", { error });
+  }
+}