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/settingsSchema.ts

@@ -87,6 +87,10 @@ export const SETTINGS_FIELD_SCHEMAS: { [K in keyof Settings]: z.ZodType<Settings
   videoFolder: trimmedWhere((v) => v === '' || isSafeOutputDir(v)),
   audioFolder: trimmedWhere((v) => v === '' || isSafeOutputDir(v)),
   filenameTemplate: trimmedWhere(isSafeFilenameTemplate),
+  // Collection folder layout (PINCHFLAT): empty = built-in default; otherwise a
+  // safe relative yt-dlp template (isSafeFilenameTemplate allows '/'-separated
+  // path segments and rejects absolute paths + '..' traversal).
+  collectionOutputTemplate: trimmedWhere((v) => v === '' || isSafeFilenameTemplate(v)),
   defaultVideoQuality: z.enum(VIDEO_QUALITY_OPTIONS),
   defaultAudioQuality: z.enum(AUDIO_QUALITY_OPTIONS),
   rateLimit: trimmedWhere((v) => RATE_LIMIT_RE.test(v)),