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/renderer/src/views/settings/FilenamesCard.tsx

@@ -6,6 +6,7 @@ import { useSettingsStyles } from './settingsStyles'
 export function FilenamesCard(): React.JSX.Element {
   const styles = useSettingsStyles()
   const filenameTemplate = useSettings((s) => s.filenameTemplate)
+  const collectionOutputTemplate = useSettings((s) => s.collectionOutputTemplate)
   const restrictFilenames = useSettings((s) => s.restrictFilenames)
   const useDownloadArchive = useSettings((s) => s.useDownloadArchive)
   const update = useSettings((s) => s.update)
@@ -29,6 +30,17 @@ export function FilenamesCard(): React.JSX.Element {
         Example: {filenameTemplate.replace('%(title)s', 'My Video').replace('%(ext)s', 'mp4')}
       </Caption1>
 
+      <Field
+        label="Collection folder layout"
+        hint="How channel/playlist (Library) downloads are foldered. Leave blank for the default Channel / Playlist / Title. Power users: a raw yt-dlp -o template, e.g. %(uploader)s/%(playlist)s/%(playlist_index)s - %(title)s.%(ext)s"
+      >
+        <Input
+          value={collectionOutputTemplate}
+          placeholder="Channel / Playlist / NNN - Title (default)"
+          onChange={(_, d) => update({ collectionOutputTemplate: d.value })}
+        />
+      </Field>
+
       <Field
         label="Restrict filenames"
         hint="Sanitize titles to plain ASCII letters/digits, no spaces -- safer for old filesystems and shells."