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/shared/ipc.ts

@@ -71,7 +71,12 @@ export const IpcChannels = {
   scheduledSyncGet: 'sources:scheduled-sync-get',
   scheduledSyncSet: 'sources:scheduled-sync-set',
   /** main → renderer push channel for live indexing progress */
-  indexProgress: 'sources:index-progress'
+  indexProgress: 'sources:index-progress',
+  // --- Built-in yt-dlp terminal (Phase N) ---
+  terminalRun: 'terminal:run',
+  terminalCancel: 'terminal:cancel',
+  /** main → renderer push channel for live terminal output lines */
+  terminalOutput: 'terminal:output'
 } as const
 
 /** Sentinel format id meaning "let yt-dlp pick the best video+audio". */
@@ -147,6 +152,13 @@ export interface DownloadOptions {
   videoContainer: VideoContainer
   /** preferred video codec (sort tiebreaker, not a hard filter) */
   preferredVideoCodec: VideoCodecPref
+  /**
+   * Advanced: a raw yt-dlp `-S` format-sort string (e.g. 'res:1080,vcodec:av01,size').
+   * When non-empty it replaces the codec-derived sort, letting power users rank
+   * resolution / codec / container / size by weighted priority. Empty = use the
+   * preferredVideoCodec tiebreaker.
+   */
+  formatSort: string
   /** download + embed subtitles into video */
   embedSubtitles: boolean
   /** comma-separated yt-dlp sub-lang selectors, e.g. 'en' or 'en.*,es' */
@@ -179,6 +191,7 @@ export const DEFAULT_DOWNLOAD_OPTIONS: DownloadOptions = {
   audioFormat: 'mp3',
   videoContainer: 'mp4',
   preferredVideoCodec: 'any',
+  formatSort: '',
   embedSubtitles: false,
   subtitleLanguages: 'en',
   autoSubtitles: false,
@@ -509,6 +522,13 @@ export interface CommandTemplate {
   id: string
   name: string
   args: string
+  /**
+   * Optional regex (matched case-insensitively against the download URL). When
+   * set and custom commands are enabled, this template auto-applies to any URL it
+   * matches — taking precedence over the global defaultTemplateId. Empty/undefined
+   * means the template is only applied when explicitly chosen as the default.
+   */
+  urlPattern?: string
 }
 
 /** Result of building the exact yt-dlp command line for the current form state, without running it. */
@@ -671,3 +691,21 @@ export interface ScheduledSyncStatus {
   enabled: boolean
   error?: string
 }
+
+// --- Built-in yt-dlp terminal (Phase N) -------------------------------------
+// A power-user console that runs the bundled yt-dlp with raw, user-typed args
+// and streams its output. The binary is fixed to yt-dlp (never arbitrary exes),
+// and the feature is gated on the same customCommandEnabled consent flag as the
+// per-download extra args (extra args can run code via --exec — audit F2).
+
+/** Live output pushed on IpcChannels.terminalOutput while a terminal command runs. */
+export type TerminalEvent =
+  | { type: 'output'; id: string; line: string; stream: 'stdout' | 'stderr' }
+  | { type: 'done'; id: string; code: number | null }
+  | { type: 'error'; id: string; error: string }
+
+/** Result of starting a terminal command (pre-spawn validation only). */
+export interface TerminalRunResult {
+  ok: boolean
+  error?: string
+}