feat(feed): pick the feed's view from its own toolbar

The view mode moves out of Settings into a switcher next to sort, on the
feed and channel pages alike. It leaves the Settings prefs draft for its
own eager save: a toolbar click must not mark that page dirty and trip
its leave-page guard.

lib/feedView.ts owns the vocabulary and maps the old grid/list prefs
forward on read, so nobody's saved choice is lost.

frontend/src/components/ChannelPage.tsx

@@ -8,6 +8,7 @@ import { useConfirm } from "./ConfirmProvider";
 import { notify } from "../lib/notifications";
 import { notifyYouTubeActionError } from "../lib/youtubeErrors";
 import { api, type FeedFilters, type Me } from "../lib/api";
+import type { FeedView } from "../lib/feedView";
 import { channelYouTubeUrl, formatViews } from "../lib/format";
 
 // --- About-tab metadata helpers ---
@@ -54,6 +55,7 @@ export default function ChannelPage({
   initialName,
   me,
   view,
+  setView,
   onBack,
   onOpenChannel,
   onShowInFeed,
@@ -61,7 +63,10 @@ export default function ChannelPage({
   channelId: string;
   initialName?: string;
   me: Me;
-  view: "grid" | "list";
+  // The feed's view pref, passed straight through to the Feed this page renders — so its
+  // toolbar carries the same switcher and a change here is the same account-wide choice.
+  view: FeedView;
+  setView: (v: FeedView) => void;
   onBack: () => void;
   // Narrow the real feed to this channel and go there. Offered only for a channel you're
   // subscribed to: the feed defaults to scope "my", so filtering it to a channel you don't
@@ -371,6 +376,7 @@ export default function ChannelPage({
             filters={filters}
             setFilters={setFilters}
             view={view}
+            setView={setView}
             canRead={me.can_read}
             isDemo={me.is_demo}
             onOpenWizard={() => {}}