feat(roadmap): surface stale checkboxes + collection output-path setting

Command preview + incognito toggle were already wired end-to-end in the
DownloadBar (Show command button, Incognito checkbox) — flipped the two
stale ROADMAP.md checkboxes with notes; verified live in the preview.

Output-path setting (PINCHFLAT): new Settings.collectionOutputTemplate — a
raw yt-dlp -o template overriding the default Channel/Playlist/NNN-Title
layout for Library downloads (empty = default). collectionOutputTemplate()
takes an optional custom template (joined under outDir, left for yt-dlp to
expand); download.ts passes the setting; zod schema validates it as a safe
relative template; Settings -> Filenames field. Tests in buildArgs +
settingsSchema; live-verified the field renders.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/main/download.ts

@@ -200,10 +200,17 @@ export function buildCommand(opts: StartDownloadOptions, cookiesFile?: string):
   const perKindDir = (opts.kind === 'audio' ? settings.audioFolder : settings.videoFolder)?.trim()
   const outDir = safeOverride || perKindDir || getDefaultMediaDir(opts.kind)
   // A collection (media-manager) download is filed into <channel>/<playlist>/
-  // <NNN> - <title> folders; an ordinary download uses the flat filenameTemplate.
+  // <NNN> - <title> folders by default, or into a power-user's raw yt-dlp `-o`
+  // layout (Settings.collectionOutputTemplate); an ordinary download uses the
+  // flat filenameTemplate.
   const filenameTemplate = settings.filenameTemplate?.trim() || '%(title)s.%(ext)s'
   const outputTemplate = opts.collection
-    ? collectionOutputTemplate(outDir, opts.collection, '%(title)s.%(ext)s')
+    ? collectionOutputTemplate(
+        outDir,
+        opts.collection,
+        '%(title)s.%(ext)s',
+        settings.collectionOutputTemplate
+      )
     : join(outDir, filenameTemplate)
   // Per-download override wins; otherwise use the persisted defaults.
   const options = opts.options ?? settings.downloadOptions