perf: race GitHub proxies concurrently for driver downloads and registry fetch

Replace sequential proxy fallback (up to 30s worst-case) with concurrent
racing via futures::select_ok, returning the first successful response.
Add list_installed_agents_local command for instant UI rendering with
async registry update. Fix missing useToast import in RedisValueViewer.

src/components/config/DriverStoreDialog.vue

@@ -238,7 +238,17 @@ async function deleteJdbcDriver(path: string) {
 // ──────────── Lifecycle ────────────
 
 onMounted(async () => {
-  await refreshAgents();
+  const [jre, localDrivers] = await Promise.all([
+    invoke<boolean>("check_jre_installed"),
+    invoke<AgentDriverInfo[]>("list_installed_agents_local"),
+  ]);
+  jreInstalled.value = jre;
+  drivers.value = localDrivers;
+
+  invoke<AgentDriverInfo[]>("list_installed_agents").then((result) => {
+    drivers.value = result;
+  });
+
   unlisten = await listen<InstallProgress>("agent-install-progress", (event) => {
     if (event.payload.step === "done") {
       progress.value = null;

src/components/redis/RedisValueViewer.vue

@@ -9,6 +9,7 @@ import { Sheet, SheetContent, SheetFooter, SheetHeader, SheetTitle } from "@/com
 import DangerConfirmDialog from "@/components/editor/DangerConfirmDialog.vue";
 import * as api from "@/lib/api";
 import type { RedisValue } from "@/lib/api";
+import { useToast } from "@/composables/useToast";
 import {
   canEditRedisMemberDetail,
   clampRedisMemberDetailSheetWidth,
@@ -18,6 +19,7 @@ import {
 } from "@/lib/redisValuePresentation";
 
 const { t } = useI18n();
+const { toast } = useToast();
 
 const props = defineProps<{
   connectionId: string;