Fix W8/W9: add Ctrl+, Settings shortcut; restore focus on palette close

W8: Added Ctrl+, as a standard Settings accelerator alongside the existing
    Ctrl+K palette shortcut. The key handler now handles both in one listener
    so there's a single window.addEventListener lifecycle.

W9: Command palette now restores focus to the previously focused element when
    it closes. prePaletteRef stores document.activeElement at open time;
    onClose fires a requestAnimationFrame focus-restore after unmounting the
    palette, so the focus returns to the trigger (a sidebar nav button, the
    URL input, etc.) rather than leaving focus stranded at the document body.

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, useRef } from 'react'
 import { FluentProvider, makeStyles, tokens } from '@fluentui/react-components'
 import { Sidebar, type TabValue } from './components/Sidebar'
 import { DownloadsView } from './components/DownloadsView'
@@ -42,13 +42,19 @@ function App(): React.JSX.Element {
   const isDark = useResolvedDark()
   const [tab, setTab] = useState<TabValue>('downloads')
   const [paletteOpen, setPaletteOpen] = useState(false)
+  // Track the element that was focused before the palette opened so we can restore it on close.
+  const prePaletteRef = useRef<Element | null>(null)
 
-  // Ctrl/Cmd+K toggles the command palette.
+  // Ctrl+K: command palette. Ctrl+,: Settings. (W8/W9)
   useEffect(() => {
     function onKey(e: KeyboardEvent): void {
       if ((e.ctrlKey || e.metaKey) && (e.key === 'k' || e.key === 'K')) {
         e.preventDefault()
+        prePaletteRef.current = document.activeElement
         setPaletteOpen((o) => !o)
+      } else if (e.ctrlKey && e.key === ',') {
+        e.preventDefault()
+        setTab('settings')
       }
     }
     window.addEventListener('keydown', onKey)
@@ -179,7 +185,14 @@ function App(): React.JSX.Element {
             </main>
 
             {paletteOpen && (
-              <CommandPalette actions={paletteActions} onClose={() => setPaletteOpen(false)} />
+              <CommandPalette
+                actions={paletteActions}
+                onClose={() => {
+                  setPaletteOpen(false)
+                  const el = prePaletteRef.current
+                  if (el instanceof HTMLElement) requestAnimationFrame(() => el.focus())
+                }}
+              />
             )}
           </>
         )}