Clarify group-chat scraping and refresh puppet URLs via the core

poc/public/media.js

@@ -118,8 +118,10 @@
         document.querySelector("#scope-bot")?.classList.remove("active");
     }
 
-    async function loadChannels() {
-        if (state.loadedChannels) return;
+    async function loadChannels(force = false) {
+        if (state.loadedChannels && !force) return;
+        state.dmsError = null;
+
         try {
             const data = await window.VK.api.get("/api/state");
             state.guilds = data?.guilds ?? [];
@@ -150,14 +152,16 @@
                         label: `${dm.name || names || "DM"} (${dm.type === 3 ? "group DM" : "DM"})`
                     });
                 }
-            } catch {
+            } catch (error) {
                 state.dms = [];
+                state.dmsError = error.message;
             }
 
             state.loadedChannels = true;
-        } catch {
+        } catch (error) {
             state.guilds = [];
             state.channels = [];
+            state.dmsError = error.message;
         }
     }
 
@@ -844,6 +848,16 @@
         tree.replaceChildren();
 
         if (scrapeTab === "group") {
+            if (state.dmsError) {
+                hint.textContent = `Group chats need the core client: ${state.dmsError}`;
+                tree.append(
+                    button("Retry", () => {
+                        void loadChannels(true).then(renderScrapeTree);
+                    })
+                );
+                return;
+            }
+
             const groups = state.dms.filter(dm => dm.type === 3);
             hint.textContent = groups.length ? "Group chats use the puppet account." : "No cached group chats yet.";
             for (const dm of groups) {
@@ -881,7 +895,7 @@
     function openScrapeModal() {
         renderScrapeTree();
         scrapeModal.hidden = false;
-        void loadChannels().then(renderScrapeTree);
+        void loadChannels(true).then(renderScrapeTree);
     }
 
     for (const [tab, id] of [