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/AuditLog.tsx

@@ -14,6 +14,7 @@ import { LoadingState, StateMessage } from "./ui/QueryState";
 import { auditColumns } from "./auditColumns";
 import { notifyActionError } from "../lib/actionErrors";
 import { compareText } from "../lib/collate";
+import { foldJobRuns } from "../lib/auditGroups";
 
 // Admin-only audit trail: an append-only who/what/when log of admin actions + scheduler run
 // summaries (never per-row). Read-only apart from Clear. Client-side sort/filter/paginate via
@@ -25,7 +26,8 @@ export default function AuditLog() {
   const confirm = useConfirm();
   const q = useQuery({ queryKey: qk.adminAudit(), queryFn: () => api.adminAudit() });
   const data = q.data;
-  const rows = useMemo(() => data?.items ?? [], [data]);
+  // Back-to-back successful runs of one job fold into one row (lib/auditGroups, E31).
+  const rows = useMemo(() => foldJobRuns(data?.items ?? []), [data]);
 
   const actionOptions = useMemo(() => {
     // By what the reader sees — the named action, in their alphabet — not by the code.