fix(frontend): emptied chat keeps its storage head, shared-only chat explains why nothing can be bulk moved, back from a chat returns to the same place in the list, cleanup wording agrees in number

frontend/src/lib/stores/storage.svelte.ts

@@ -2,9 +2,15 @@ import { ui } from "#lib/stores/ui.svelte.js";
 
 export type StorageListing = "files" | "chats";
 
+interface Resume {
+  count: number;
+  top: number;
+}
+
 function createStorageUi() {
   let listing = $state<StorageListing>("files");
   let chatId = $state<number | null>(null);
+  let resume: Resume | null = null;
 
   return {
     get chatId() {
@@ -16,10 +22,16 @@ function createStorageUi() {
     set listing(next: StorageListing) {
       listing = next;
     },
-    openChat(id: number) {
+    openChat(id: number, from: Resume) {
       chatId = id;
+      resume = from;
       ui.openPanel("storage-chat");
     },
+    takeResume(): Resume | null {
+      const taken = resume;
+      resume = null;
+      return taken;
+    },
   };
 }