Fix SR8: update window title to reflect active download state

The window title was always 'AeroFetch' regardless of activity, so screen
readers and taskbar previews couldn't tell whether downloads were running.

The taskbarProgress IPC handler (which already fires on each progress tick)
now calls mainWindow.setTitle() alongside setProgressBar/setOverlayIcon:
- Idle: 'AeroFetch'
- Downloading: 'AeroFetch -- N downloads active'
- Error: 'AeroFetch -- Error'

This reuses the same overlay badge label string so the text is consistent
between the taskbar tooltip and the title bar.

typecheck + 242 tests green.

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

src/main/index.ts

@@ -435,12 +435,13 @@ function registerIpcHandlers(): void {
   ipcMain.handle(IpcChannels.scheduledSyncGet, () => getScheduledSync())
   ipcMain.handle(IpcChannels.scheduledSyncSet, (_e, enabled: boolean) => setScheduledSync(enabled))
 
-  // Reflect overall queue progress on the Windows taskbar.
+  // Reflect overall queue progress on the Windows taskbar and window title (SR8).
   ipcMain.handle(IpcChannels.taskbarProgress, (_e, p: TaskbarProgress) => {
     if (!mainWindow || mainWindow.isDestroyed()) return
     if (p.mode === 'none') {
       mainWindow.setProgressBar(-1)
       mainWindow.setOverlayIcon(null, '')
+      mainWindow.setTitle('AeroFetch')
     } else {
       mainWindow.setProgressBar(Math.max(0, Math.min(1, p.fraction)), { mode: p.mode })
       const badge = p.mode === 'error' ? getErrorBadge() : getActiveBadge()
@@ -448,6 +449,7 @@ function registerIpcHandlers(): void {
       const label =
         p.mode === 'error' ? 'Download error' : `${n} download${n !== 1 ? 's' : ''} active`
       mainWindow.setOverlayIcon(badge, label)
+      mainWindow.setTitle(p.mode === 'error' ? 'AeroFetch — Error' : `AeroFetch — ${label}`)
     }
   })