perf(media): optimize YouTube metadata loading

src/components/AddDownloadsModal.tsx

@@ -6,6 +6,7 @@ import { open } from '@tauri-apps/plugin-dialog';
 import { invokeCommand as invoke } from '../ipc';
 import { DuplicateResolutionModal, DuplicateConflict } from './DuplicateResolutionModal';
 import { categoryForFileName, fileNameFromUrl, isMediaUrl } from '../utils/downloads';
+import { fetchMediaMetadataDeduped } from '../utils/mediaMetadata';
 
 interface RawMediaFormat {
   format_id?: string;
@@ -371,8 +372,8 @@ export const AddDownloadsModal = () => {
               }
             }
 
-            const mediaData = await invoke('fetch_media_metadata', {
-              url, 
+            const mediaData = await fetchMediaMetadataDeduped({
+              url,
               cookieBrowser: browserArg,
               username: login?.username || null,
               password: keychainPassword

src/store/useDownloadStore.ts

@@ -12,6 +12,7 @@ import type { Queue } from '../bindings/Queue';
 import type { MediaMetadata } from '../bindings/MediaMetadata';
 import { useSettingsStore } from './useSettingsStore';
 import { isActiveDownloadStatus, redactDownloadForPersistence } from '../utils/downloads';
+import { fetchMediaMetadataDeduped } from '../utils/mediaMetadata';
 
 export type { DownloadCategory } from '../utils/downloads';
 
@@ -190,7 +191,7 @@ export const useDownloadStore = create<DownloadState>((set, get) => ({
     set({ isParsing: true, parsingError: null, activeMetadata: null, activeMetadataUrl: url });
     try {
       const settings = useSettingsStore.getState();
-      const metadata = await invoke('fetch_media_metadata', { 
+      const metadata = await fetchMediaMetadataDeduped({
         url,
         cookieBrowser: settings.mediaCookieSource === 'none' ? null : settings.mediaCookieSource,
         username: null,

src/utils/mediaMetadata.ts

@@ -0,0 +1,27 @@
+import { invokeCommand as invoke } from '../ipc';
+import type { MediaMetadata } from '../bindings/MediaMetadata';
+
+type FetchMediaMetadataArgs = {
+  url: string;
+  cookieBrowser: string | null;
+  username: string | null;
+  password: string | null;
+};
+
+const inFlightMediaMetadata = new Map<string, Promise<MediaMetadata>>();
+
+const metadataKey = (args: FetchMediaMetadataArgs) =>
+  JSON.stringify([args.url, args.cookieBrowser, args.username, args.password]);
+
+export const fetchMediaMetadataDeduped = (args: FetchMediaMetadataArgs): Promise<MediaMetadata> => {
+  const key = metadataKey(args);
+  const existing = inFlightMediaMetadata.get(key);
+  if (existing) return existing;
+
+  const request = invoke('fetch_media_metadata', args)
+    .finally(() => {
+      inFlightMediaMetadata.delete(key);
+    });
+  inFlightMediaMetadata.set(key, request);
+  return request;
+};