fix(e24): review round 2 — a buried history entry, a stale hero, and a spinner that was not ours

Nine of the round's ten surviving findings. The tenth (a failed shelf reorder leaving an
order the server rejected on screen) is on ROADMAP.md: its obvious remedy reintroduces the
overlapping-move defect the code already documents, so it wants a design, not a review edit.

- `navigateOverOverlays` buried the live overlay entries before knowing whether the
  navigation pushed one. `setPage` no-ops when the page is already current and Home is the
  default landing page, so Shift+W over a player ON Home marked its entry buried under a
  push that never happened: the unmount consumed the mark instead of reclaiming the entry,
  and the next browser Back was a press that did nothing. `setPage` now reports whether it
  navigated, and one `buryUnder` rule serves both entry points — `closeThenNavigate` takes
  the same no-op navigation from a palette command for the page you are already on.
- The hero could answer a new time budget with the previous one's pick. The chip row resets
  seed/seen/press but cannot reset an answer that already resolved, and `keepPreviousData`
  chained through the disabled seed-0 query — so a reroll under "10 perc" showed the film
  picked for "Bármennyi" while it loaded, and kept it if the request failed. `lastPick` now
  carries the server's own budget echo, and the placeholder is scoped to the budget.
- The reroll button spun and swallowed clicks after mark-watched, bookmark, pin and shelf
  moves: the pick key sits under the invalidated `discover` prefix on purpose, so raw
  `isFetching` was true for background refetches. It now means "a press of mine is
  outstanding" — which still covers the first press, where there is no placeholder.
- Failed writes on Home toasted the page's LOAD-failure string over a fully loaded page;
  they get their own key (HU+EN). The empty-state reroll had no `loading`, so the press was
  unacknowledged and a second click skipped a tier. `danger` moved into the shared unpin row
  so the same command is not red on the shelf and neutral in the rail below it.
- Two comments claimed things the code does not do: the `exclude` cap guards no "unbounded
  scan" (it never reaches SQL), and the route test that named the cap sends three keys.

Tests: the burial rule gets its own file (it is the one assertion that lets a reconcile
issue a real programmatic back()); App's keymap wiring gets a source contract, because
dropping it left all 818 tests green; `add_pin`'s IntegrityError arm was reached by nothing.
Every new test mutation-checked red, both edges where the predicate has two.

Gate: ruff, ruff format, 3x tsc, eslint (0 errors), prettier, knip, vitest 822, pytest 1005.

frontend/src/components/NavigationProvider.tsx

@@ -37,7 +37,10 @@ export interface NavigationState {
 }
 
 export interface NavigationActions {
-  setPage: (next: Page) => void;
+  /** Switch modules. Returns whether it actually navigated — it is a no-op when the requested page
+   *  is already current with no channel page over it, and a caller that buries overlay history
+   *  entries under the push has to know that (see `lib/history.navigateOverOverlays`). */
+  setPage: (next: Page) => boolean;
   openChannel: (id: string, name?: string) => void;
   closeChannel: () => void;
   enterYtSearch: (q: string) => void;
@@ -50,7 +53,7 @@ const StateContext = createContext<NavigationState>({
   ytSearch: null,
 });
 const ActionsContext = createContext<NavigationActions>({
-  setPage: () => {},
+  setPage: () => false,
   openChannel: () => {},
   closeChannel: () => {},
   enterYtSearch: () => {},
@@ -118,7 +121,7 @@ export function NavigationProvider({ children }: { children: ReactNode }) {
     (next: Page) => {
       // A channel page overlays the content column, so a nav click must close it even when the
       // underlying page is unchanged (e.g. "Feed" while a channel opened from the feed).
-      if (next === pageRef.current && !channelViewRef.current) return;
+      if (next === pageRef.current && !channelViewRef.current) return false;
       markDirty();
       setChannelView(null); // leave any open channel page when navigating via the rail
       setPageState(next);
@@ -147,6 +150,7 @@ export function NavigationProvider({ children }: { children: ReactNode }) {
         }),
       );
       notifyNav();
+      return true;
     },
     [markDirty],
   );