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/lib/storage.ts

@@ -17,6 +17,9 @@ export const LS = {
   defaultViewFilters: "siftlode.defaultViewFilters",
   page: "siftlode.page",
   perfMode: "siftlode.perfMode",
+  // The feed's view mode (see lib/feedView.ts). A local cache of the server pref, so the feed
+  // renders in your chosen view on first paint instead of flashing the default.
+  feedView: "siftlode.feedView",
   channelFilter: "siftlode.channelFilter",
   channelsView: "siftlode.channelsView",
   channelsTable: "siftlode.channelsTable",