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/App.tsx

@@ -145,7 +145,9 @@ export default function App() {
   // Through `navigateOverOverlays`, because a global key can fire while an overlay is open and does
   // not know it: the page change unmounts the player (it lives inside the module), whose reconcile
   // then reclaimed the entry this push had just made — Shift+W over a playing video closed the
-  // player and snapped straight back to the feed.
+  // player and snapped straight back to the feed. `setPage`'s boolean is load-bearing here, not
+  // decoration: pressed while ALREADY on Home (the default landing page) it navigates nowhere, and
+  // burying the open player's entry under a push that never happened orphaned it — see `buryUnder`.
   useGlobalKeymap(!!meQuery.data, () => navigateOverOverlays(() => setPage("home")));
 
   // Pin this tab to whatever account it first loaded as. Without this, a tab that never picked