chore: lint core/react with eslint-plugin-react-hooks (#2192)

`eslint-plugin-react-hooks` was a `clients/web` devDependency only, and each
client's `eslint .` is scoped to its own directory — so the whole hook rule
set had never looked at `core/react/`, a directory of nothing but React
hooks. "Neither surface has JSX" was the stated reason and was never a good
one: the rules judge hooks, not JSX.

Add the plugin at the root and apply it in a `core/react/**` block (scoped
there rather than to all of `core/**`, since the rules key off the `use`
prefix), with `exhaustive-deps` promoted to `error` as `clients/web` does.

Resolve the 15 findings it then reports:

- `useSettingsDraft` / `useClientSettingsDraft` seed their draft during
  render instead of in a `targetId`/`opened`-keyed effect, so the previous
  target's values never reach the DOM — the same rule `clients/web` spells
  `useValueChange`. Their "latest value" refs move from render-time writes
  into an effect; every reader (the debounce timer, `flush`, `onChange`)
  runs after a commit, so a post-commit write is what they need.
- The three async loaders keep their effects behind justified inline
  disables: `set-state-in-effect` follows a call into an async function
  without modelling the `await`, verified against a minimal hook whose only
  setState is in a continuation.
- `useInitialConfig`'s cleanup bump keeps reading `generation.current` at
  teardown — the rule's "copy it into a variable" advice would restore a
  stale request token and let a superseded response commit.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_013hzwzS8UvBsr4yZm7o7sev
Signed-off-by: cliffhall <cliff@futurescale.com>

core/react/useClientSettingsDraft.ts

@@ -33,25 +33,33 @@ export function useClientSettingsDraft<T>({
   const timerRef = useRef<ReturnType<typeof setTimeout> | undefined>(undefined);
   const latestValuesRef = useRef<T | null>(null);
 
-  const resolveInitialRef = useRef(resolveInitial);
+  // Seeded during render rather than in an effect, for the reason spelled
+  // out on {@link useSettingsDraft}: an effect would paint the previous
+  // session's draft for one frame before correcting itself. `seeded` is
+  // tracked separately from `draft` so a `resolveInitial` that legitimately
+  // returns `null` is not re-seeded on every render.
+  const [seeded, setSeeded] = useState(false);
+  if (seeded !== opened) {
+    setSeeded(opened);
+    setDraft(opened ? resolveInitial() : null);
+  }
+
   const onPersistRef = useRef(onPersist);
   const onErrorRef = useRef(onError);
   const openedRef = useRef(opened);
-  resolveInitialRef.current = resolveInitial;
-  onPersistRef.current = onPersist;
-  onErrorRef.current = onError;
-  openedRef.current = opened;
-
+  // Written in an effect rather than during render (`react-hooks/refs`).
+  // Every reader — the debounce timer, `flush`, and `onChange` — runs after
+  // a commit, so a post-commit write is what they need. `latestValuesRef`
+  // mirrors `draft` here so it is re-seeded (and cleared on close) without a
+  // second copy of the seeding rule; `onChange` still writes it
+  // synchronously, because a functional update in the same tick has to see
+  // the value the previous call produced.
   useEffect(() => {
-    if (!opened) {
-      setDraft(null);
-      latestValuesRef.current = null;
-      return;
-    }
-    const initial = resolveInitialRef.current();
-    setDraft(initial);
-    latestValuesRef.current = initial;
-  }, [opened]);
+    onPersistRef.current = onPersist;
+    onErrorRef.current = onError;
+    openedRef.current = opened;
+    latestValuesRef.current = draft;
+  });
 
   useEffect(() => {
     return () => {