feat: Phase N power-user surface (terminal, palette, per-item, sort, url-templates)

- Built-in yt-dlp terminal: src/main/terminal.ts streams raw yt-dlp runs
  (binary fixed, gated on customCommandEnabled), new TerminalView + sidebar tab
- Command palette (Ctrl/Cmd+K), portal-free CommandPalette.tsx wired in App
- Per-playlist-item editing: per-row video/audio toggle + All video/All audio
  batch; addPlaylist enqueues via addMany with per-item kind
- Weighted format sorting: DownloadOptions.formatSort -> raw -S (overrides codec)
- URL-regex template auto-matching: CommandTemplate.urlPattern + selectExtraArgs
  matchesUrl, threaded through resolveExtraArgs; field in TemplateManager

typecheck + test (192) + electron-vite build all clean. Roadmap: Phase N COMPLETE.

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

src/main/index.ts

@@ -15,6 +15,7 @@ import { getFfmpegVersions } from './ffmpeg'
 import { checkForAppUpdate, downloadAppUpdate, runAppUpdate } from './updater'
 import { probeMedia } from './probe'
 import { startDownload, cancelDownload, pauseDownload, previewCommand } from './download'
+import { runTerminal, cancelTerminal } from './terminal'
 import { getSettings, setSettings, ensureMediaDirs } from './settings'
 import { listHistory, addHistory, removeHistory, removeManyHistory, clearHistory } from './history'
 import { listTemplates, saveTemplate, removeTemplate } from './templates'
@@ -212,6 +213,10 @@ function registerIpcHandlers(): void {
   })
   ipcMain.handle(IpcChannels.downloadCancel, (_e, id: string) => cancelDownload(id))
   ipcMain.handle(IpcChannels.downloadPause, (_e, id: string) => pauseDownload(id))
+  ipcMain.handle(IpcChannels.terminalRun, (e, id: string, args: string) =>
+    runTerminal(e.sender, id, args)
+  )
+  ipcMain.handle(IpcChannels.terminalCancel, (_e, id: string) => cancelTerminal(id))
 
   ipcMain.handle(IpcChannels.defaultFolder, () => app.getPath('downloads'))