refactor(ui): the popover engine and every render-phase ref write compile under the React Compiler

E32 S3. The compiler skipped 93 functions; it now skips 29 (try/finally shapes, two suppressions,
VirtualGrid). react-hooks/refs hits 245 -> 31.

- Popover engine: `ref={pop.refs.setReference}` made the compiler treat the whole popover handle as
  a ref, so every component holding one was skipped (21 call sites, the engine and its surface
  among them). The setter is destructured now; the same for useScrollFade and useReturnFocus.
- Render-phase `ref.current = x` writes moved to `useEffectEvent` where only effects read them,
  else to the new `useLatest` (written in a layout effect) / `useStableCallback`.
- FocusSafeButton (under every Button) read the focused element during render; it reads it through
  useSyncExternalStore, which React asks on every render instead of a cached memo.

Bugs this surfaced, fixed:
- Combobox: a chip could keep showing its raw id. The label cache was a ref an effect filled after
  the render that needed it; it is state merged during render now (test seen RED).
- useUndoable rendered from a ref plus a forced re-render; compiled, that memoizes a stale value.
  The history is state now, mirrored in a ref for the stable callbacks.
- ConfigPanel and the saved-views editor re-seeded their drafts in an effect, painting the stale
  draft for a frame; both adjust during render against the remembered key.
- Toaster's handover is written after commit instead of during render; a new test pins that the
  inherited set is taken once, at the takeover (seen RED on a per-render re-read).
- IssueComposer mutated a ref prop as a one-shot focus token; it is plain state.
- PlexBrowse wrote its info-scroll memory from an effect declared before the ref, past its own
  "one writer" rule; the writer comes first now and the effect goes through it.

The compiler ratchet drops to the measured 29 and now also requires FocusSafeButton and the popover
engine to compile.

frontend/src/lib/plexPlayerHooks.ts

@@ -16,6 +16,7 @@ import {
 } from "./fullscreen";
 import { api, type PlexItemDetail, type PlexMarker } from "./api";
 import { qk } from "./queryKeys";
+import { useLatest } from "./useLatest";
 import i18n, { plexLang } from "../i18n";
 import { type PlexPlayerPrefs } from "./plexPlayerPrefs";
 import { PLEX_SCALE, normalizeVolumeIn, stepVolumeIn } from "./playerVolume";
@@ -458,17 +459,13 @@ export function useAutoSkip(opts: {
     seekTo,
     videoRef,
   } = opts;
-  const skipProgressRef = useRef<number | null>(null);
-  const cancelAutoSkipRef = useRef<() => void>(() => {});
-
   const activeMarker: PlexMarker | undefined = markers?.find(
     (m) => abs >= m.start_s && abs < m.end_s - 1,
   );
-  const activeMarkerRef = useRef(activeMarker);
-  activeMarkerRef.current = activeMarker;
+  const activeMarkerRef = useLatest(activeMarker);
 
   const [skipProgress, setSkipProgress] = useState<number | null>(null);
-  skipProgressRef.current = skipProgress;
+  const skipProgressRef = useLatest(skipProgress);
   const cancelledMarkerRef = useRef<string | null>(null);
   // Forget a cancelled-skip when the item changes: the ref holds a `${type}-${start_s}` key, and a
   // marker at the same offset on the NEXT episode would otherwise be suppressed by a cancel made on
@@ -479,8 +476,7 @@ export function useAutoSkip(opts: {
   // The running countdown interval, so cancelAutoSkip can actually STOP it — clearing skipProgress
   // alone left the interval ticking, which re-set the progress ~100ms later and skipped anyway.
   const skipTimerRef = useRef<number | null>(null);
-  const reportWatchedErrorRef = useRef(opts.reportWatchedError);
-  reportWatchedErrorRef.current = opts.reportWatchedError;
+  const reportWatchedErrorRef = useLatest(opts.reportWatchedError);
   const doSkip = useCallback(
     (m: PlexMarker) => {
       setSkipProgress(null);
@@ -495,7 +491,7 @@ export function useAutoSkip(opts: {
         go(nextId, watchedWrite);
       } else seekTo(m.end_s);
     },
-    [id, go, nextId, seekTo],
+    [id, go, nextId, seekTo, reportWatchedErrorRef],
   );
   const cancelAutoSkip = useCallback(() => {
     const m = activeMarkerRef.current;
@@ -505,8 +501,8 @@ export function useAutoSkip(opts: {
       skipTimerRef.current = null;
     }
     setSkipProgress(null);
-  }, []);
-  cancelAutoSkipRef.current = cancelAutoSkip;
+  }, [activeMarkerRef]);
+  const cancelAutoSkipRef = useLatest(cancelAutoSkip);
   // The marker is identified by type+offset rather than by object identity: `markers?.find` returns
   // the same element while the playhead stays inside it, but a refetch of the markers list would
   // hand back an equal-but-new object and restart a countdown already under way. The marker itself
@@ -548,6 +544,7 @@ export function useAutoSkip(opts: {
     autoSkipDelay,
     doSkip,
     videoRef,
+    activeMarkerRef,
   ]);
 
   return { activeMarker, skipProgress, skipProgressRef, cancelAutoSkipRef, doSkip };