Fix L19/L73: replace setTimeout focus hack with double-rAF; unify probe verb

L19: App.tsx replaced `setTimeout(() => focus(), 60)` in the "New download"
     palette action with `requestAnimationFrame(() => requestAnimationFrame(...))`
     to wait exactly one React render + paint cycle rather than an arbitrary 60ms
     timer that could race on slow machines.

L73: DownloadBar's probe button label changed from "Fetch" to "Check URL" (hint
     and aria-label both updated). Placeholder text updated to match. This
     distinguishes it from LibraryView's "Index" action, which catalogs an entire
     channel/playlist, making both labels clearly meaningful in context.

typecheck + 242 tests green.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/renderer/src/App.tsx

@@ -1,4 +1,4 @@
-import { useState, useEffect, useMemo } from 'react'
+import { useState, useEffect, useMemo } from 'react'
 import { FluentProvider, makeStyles, tokens } from '@fluentui/react-components'
 import { Sidebar, type TabValue } from './components/Sidebar'
 import { DownloadsView } from './components/DownloadsView'
@@ -57,7 +57,7 @@ function App(): React.JSX.Element {
 
   // Mirror overall queue progress onto the Windows taskbar. Subscribe to the store
   // directly (not via a selector) so taskbar updates don't re-render the app.
-  // Compare against the last IPC call and skip when nothing changed — the store
+  // Compare against the last IPC call and skip when nothing changed -- the store
   // fires on every progress tick and this avoids one IPC roundtrip per tick (L25).
   useEffect(() => {
     let lastFraction = -1
@@ -80,7 +80,7 @@ function App(): React.JSX.Element {
     return useDownloads.subscribe((st) => push(st.items))
   }, [])
 
-  // Memoized so CommandPalette sees a stable array reference between renders —
+  // Memoized so CommandPalette sees a stable array reference between renders --
   // only rebuilds when the theme label needs to change (L32).
   const paletteActions = useMemo<PaletteAction[]>(
     () => [
@@ -110,8 +110,10 @@ function App(): React.JSX.Element {
         hint: 'Focus URL',
         run: () => {
           setTab('downloads')
-          // Wait for the download bar to mount after the tab switch, then focus.
-          setTimeout(() => document.getElementById('aerofetch-url')?.focus(), 60)
+          // Double-rAF waits for React's re-render + the browser's paint before focusing.
+          requestAnimationFrame(() =>
+            requestAnimationFrame(() => document.getElementById('aerofetch-url')?.focus())
+          )
         }
       },
       {

src/renderer/src/components/DownloadBar.tsx

@@ -555,17 +555,17 @@ export function DownloadBar(): React.JSX.Element {
             if (info || probeError || playlist) download()
             else void fetchFormats()
           }}
-          placeholder="Paste a video or playlist URL, then fetch…"
+          placeholder="Paste a video or playlist URL, then check…"
           size="large"
           contentBefore={<ArrowDownloadRegular />}
         />
-        <Hint label="Fetch formats / playlist" placement="bottom" align="end">
+        <Hint label="Check URL" placement="bottom" align="end">
           <Button
             size="large"
             icon={probing ? <Spinner size="tiny" /> : <SearchRegular />}
             onClick={fetchFormats}
             disabled={!url.trim() || probing}
-            aria-label="Fetch formats or playlist"
+            aria-label="Check URL for formats or playlist"
           />
         </Hint>
         <Hint label="Paste from clipboard" placement="bottom" align="end">