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/useDismiss.ts

@@ -1,4 +1,4 @@
-import { useEffect, useRef, type RefObject } from "react";
+import { useEffect, useEffectEvent, type RefObject } from "react";
 import { useLayer } from "./layerStack";
 
 /** While `active`, close (call `onClose`) on Escape or a mousedown outside ALL of the given
@@ -26,26 +26,22 @@ export function useDismiss(
 
   // Outside-press stays per-instance (the refs/positioning are the caller's): close on a mousedown
   // that lands outside every registered element.
-  // Both arguments are read through refs so the listener can stay subscribed once per open/close —
+  // Both arguments are read through an effect event so the listener can stay subscribed once per open/close —
   // which is the point of the `[active]` dep list — without going STALE. The disabled dep list this
   // replaces asserted that onClose was "read fresh from this run's closure"; it was not. The closure
   // is built when `active` last flipped, so a caller that re-rendered with a different handler while
   // the popover stayed open kept getting the old one called (regression test in useDismiss.dom.test).
   // `refs` is the weaker case — the ref OBJECTS are stable, so a late-mounting node is seen either
   // way — but a caller that changes WHICH refs it passes while open was equally ignored.
-  const onCloseRef = useRef(onClose);
-  onCloseRef.current = onClose;
-  const refsRef = useRef(refs);
-  refsRef.current = refs;
+  const onPress = useEffectEvent((e: MouseEvent) => {
+    const list = Array.isArray(refs) ? refs : [refs];
+    const target = e.target as Node;
+    if (!list.some((r) => r.current?.contains(target))) onClose();
+  });
 
   useEffect(() => {
     if (!active) return;
-    const onDown = (e: MouseEvent) => {
-      const current = refsRef.current;
-      const list = Array.isArray(current) ? current : [current];
-      const target = e.target as Node;
-      if (!list.some((r) => r.current?.contains(target))) onCloseRef.current();
-    };
+    const onDown = (e: MouseEvent) => onPress(e);
     document.addEventListener("mousedown", onDown);
     return () => {
       document.removeEventListener("mousedown", onDown);