Complete Phase C (custom commands & yt-dlp updater) and Phase D (library, UX & notifications)

Phase C had been implemented in the working tree but never committed:
named custom-command templates (CRUD + per-download override), command
preview, and the in-app yt-dlp self-updater.

Phase D adds: history search/kind-filter/multi-select/bulk-delete/
re-download; native OS notifications on completion/failure; a private/
incognito download mode that skips history; settings+template backup/
restore via JSON; and a persistent error log surfaced as a Diagnostics
report in Settings.

See ROADMAP.md for the full per-item breakdown.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/preload/index.ts

@@ -2,6 +2,8 @@ import { contextBridge, ipcRenderer, type IpcRendererEvent } from 'electron'
 import {
   IpcChannels,
   type YtdlpVersionResult,
+  type YtdlpUpdateChannel,
+  type YtdlpUpdateResult,
   type ProbeResult,
   type StartDownloadOptions,
   type StartDownloadResult,
@@ -9,7 +11,12 @@ import {
   type Settings,
   type HistoryEntry,
   type CookiesStatus,
-  type CookiesLoginResult
+  type CookiesLoginResult,
+  type CommandTemplate,
+  type CommandPreviewResult,
+  type ErrorLogEntry,
+  type BackupExportResult,
+  type BackupImportResult
 } from '@shared/ipc'
 
 // The surface exposed to the renderer. Keep this thin: it only forwards to IPC.
@@ -49,6 +56,9 @@ const api = {
   removeHistory: (id: string): Promise<HistoryEntry[]> =>
     ipcRenderer.invoke(IpcChannels.historyRemove, id),
 
+  removeManyHistory: (ids: string[]): Promise<HistoryEntry[]> =>
+    ipcRenderer.invoke(IpcChannels.historyRemoveMany, ids),
+
   clearHistory: (): Promise<HistoryEntry[]> => ipcRenderer.invoke(IpcChannels.historyClear),
 
   /** Open the built-in sign-in window; resolves once the user closes it. */
@@ -59,6 +69,31 @@ const api = {
 
   cookiesClear: (): Promise<void> => ipcRenderer.invoke(IpcChannels.cookiesClear),
 
+  listTemplates: (): Promise<CommandTemplate[]> => ipcRenderer.invoke(IpcChannels.templatesList),
+
+  saveTemplate: (template: CommandTemplate): Promise<CommandTemplate[]> =>
+    ipcRenderer.invoke(IpcChannels.templatesSave, template),
+
+  removeTemplate: (id: string): Promise<CommandTemplate[]> =>
+    ipcRenderer.invoke(IpcChannels.templatesRemove, id),
+
+  /** Build the exact yt-dlp command line for the given form state, without running it. */
+  previewCommand: (opts: StartDownloadOptions): Promise<CommandPreviewResult> =>
+    ipcRenderer.invoke(IpcChannels.commandPreview, opts),
+
+  updateYtdlp: (channel: YtdlpUpdateChannel): Promise<YtdlpUpdateResult> =>
+    ipcRenderer.invoke(IpcChannels.ytdlpUpdate, channel),
+
+  listErrorLog: (): Promise<ErrorLogEntry[]> => ipcRenderer.invoke(IpcChannels.errorLogList),
+
+  clearErrorLog: (): Promise<ErrorLogEntry[]> => ipcRenderer.invoke(IpcChannels.errorLogClear),
+
+  /** Opens a save dialog and writes settings + templates to the chosen JSON file. */
+  exportBackup: (): Promise<BackupExportResult> => ipcRenderer.invoke(IpcChannels.backupExport),
+
+  /** Opens an open dialog and restores settings + templates from the chosen JSON file. */
+  importBackup: (): Promise<BackupImportResult> => ipcRenderer.invoke(IpcChannels.backupImport),
+
   /** Subscribe to live download events. Returns an unsubscribe function. */
   onDownloadEvent: (cb: (ev: DownloadEvent) => void): (() => void) => {
     const listener = (_e: IpcRendererEvent, ev: DownloadEvent): void => cb(ev)