fix(feed): unblock UI during fetch-more and drop indicator label text

loadMoreEpisodesForFeed's hot-cache path ran fully synchronously (no
await between getFeed and setFeeds), so the isLoadingMore spinner never
painted and keyboard input froze through every feed in a loadMoreAllFeeds
batch. Add await yieldToUI() before the setFeeds so the renderer gets a
macrotask turn to paint and process input between feeds.

Drop the "Loading…/Refreshing…/Downloading N" label text from the global
activity indicator — render the braille spinner only, per request.

src/stores/feed.ts

@@ -781,6 +781,13 @@ function createFeedStore() {
 		episodeLoadCount.set(feedId, newCount);
 		const episodes = cached.slice(0, newCount);
 
+		// Yield a real macrotask turn before the sync state update so the
+		// renderer paints the spinner and processes keyboard input before the
+		// (potentially large, per-feed in loadMoreAllFeeds) setFeeds + sort
+		// runs. Without this, the whole body executes in one microtask batch
+		// and the UI freezes through every feed in the batch.
+		await yieldToUI();
+
 		setFeeds((prev) => {
 			const updated = prev.map((f) =>
 				f.id === feedId ? { ...f, episodes } : f,