feat(ui): E31 S4a — rail rows are links, the channel page opens on unwatched, users and audit tidied

- Nav rail page rows are real links (/?page=<id>): a middle-click or
  Ctrl-click opens the page in a new tab; a plain click stays in-app.
- A fresh channel page shows the unwatched videos; a picked watch state
  is a remembered preference (channelShow).
- Users: the role, suspend and delete move into the row's one menu
  (the "…", right-click, Shift+F10); locked ones keep their reason.
- Audit log: back-to-back successful runs of one job fold into one row
  that opens to the earlier ones; a failed run reads in the danger colour.
- DESIGN.md decision log: the E31 picks.

frontend/src/components/ChannelPage.tsx

@@ -29,6 +29,9 @@ import ChannelAboutContent from "./ChannelAbout";
 import { PageToolbar } from "./ui/PageShell";
 import { PageToolbarSlot } from "./ui/pageToolbarSlot";
 import { useFeedFilters } from "./feedFiltersContext";
+import { SHOW_IDS } from "./feedFiltersInit";
+import { usePref } from "../lib/usePref";
+import { LS } from "../lib/storage";
 import { useConfirm } from "./confirmContext";
 import { notify } from "../lib/notifications";
 import { notifyYouTubeActionError } from "../lib/youtubeErrors";
@@ -260,7 +263,13 @@ export default function ChannelPage({
 
   // Channel-scoped feed: the whole catalog filtered to this channel (scope=all + source=all so
   // the explored, per-user-private videos show — the backend gates them to this explorer).
-  const [filters, setFilters] = useState<FeedFilters>(() => ({
+  // The watch state is the one filter a channel page remembers (the owner, E31): a fresh page shows
+  // what is still unwatched, and a change sticks — across channels, reloads and devices.
+  const [show, setShow] = usePref<string>("channelShow", "unwatched", {
+    localKey: LS.channelShow,
+    parse: (v) => (typeof v === "string" && SHOW_IDS.includes(v) ? v : "unwatched"),
+  });
+  const [ownFilters, setOwnFilters] = useState<FeedFilters>(() => ({
     tags: [],
     tagModes: DEFAULT_TAG_MODES,
     q: "",
@@ -271,9 +280,14 @@ export default function ChannelPage({
     includeNormal: globalFilters.includeNormal,
     includeShorts: globalFilters.includeShorts,
     includeLive: globalFilters.includeLive,
-    show: "all",
+    show: "unwatched",
     channelIds: [channelId],
   }));
+  const filters: FeedFilters = { ...ownFilters, show };
+  const setFilters = (next: FeedFilters) => {
+    if (next.show !== show) setShow(next.show);
+    setOwnFilters(next);
+  };
 
   const name = ch?.title ?? initialName ?? channelId;
   const ytUrl = channelYouTubeUrl(channelId, ch?.handle);