feat(config+ux): batch #5 — source maps, integration script, copy, redownload options

Clean config/copy items (Phase 7):
- L170: build.sourcemap 'hidden' on main/preload/renderer — emit .map for offline
  crash symbolication (of the CC8 logger's raw stacks) without exposing them.
- L34: add `test:integration` npm script (AEROFETCH_REAL_DOWNLOAD=1) for the opt-in
  real-download suite; stays out of `npm test` (needs network + live yt-dlp).
- L87: HistoryEntry carries the original `options`; redownload replays them so a
  re-download reproduces the same post-processing instead of the current defaults.
- L96: folder "Browse" buttons -> "Browse…" (they open the OS picker).
- L97: PO-token placeholder "(none)" -> "Optional -- paste a token" (consistent).
- Ticked already-resolved: L99 (M28 aria-label), L113 (UX2 tooltip=aria-label),
  L95 (usage follows verb/modifier rule), L172 (skipLibCheck accepted).

typecheck + 268 tests + eslint + prettier green (touched files LF/clean).

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

src/shared/ipc.ts

@@ -731,6 +731,10 @@ export interface HistoryEntry {
   filePath?: string
   sizeLabel?: string
   thumbnail?: string
+  /** The per-download post-processing options used originally, carried so a
+   *  re-download reproduces the same output (subtitles, SponsorBlock, container,
+   *  codec, …) instead of silently falling back to the current global defaults (L87). */
+  options?: DownloadOptions
   /** epoch milliseconds */
   completedAt: number
 }