Enable Zustand (proposal #5) + convert isCreatingRoom singleton

Phase 2 of the refactor plan in docs/ARCHITECTURE.md.

Install
- yarn add zustand (^5, matches React 19 peer requirement).

Wiring
- src/state/createNitroStore.ts: replaces the previous prototype
  (which threw on call) with a re-export of zustand's `create` under
  the project-local name `createNitroStore`. Comments document the
  convention (one store per domain, subscribe to slices not the whole
  store).

First migration target
- src/components/navigator/views/navigatorRoomCreatorStore.ts (new):
  a Zustand store with `isCreating: boolean` and `beginCreate()` —
  the latter latches the flag to true, dispatches an internal
  setTimeout to auto-reset after 5s, and replaces any in-flight timer
  on re-entry. The timer handle lives in the store's closure, so a
  remount of the view doesn't reset the lockout and StrictMode's
  double-mount no longer schedules two pending timers.
- src/components/navigator/views/NavigatorRoomCreatorView.tsx:
  removes the two module-level `let` variables that the React Compiler
  was flagging ("Writing to a variable defined outside a component is
  not allowed"). The component now reads `isCreating` via a slice
  subscription and calls `beginCreate()` from the click handler. The
  imperative guard (`if (isCreating) return`) uses
  `useRoomCreatorStore.getState()` so it reads the latest value
  synchronously without being a stale closure.
- Also cleans up `FC<{}>` -> `FC` while touching the file.

Verification
- yarn eslint on the three touched files: 1 pre-existing error
  (the `setCategory(categories[0].id)` set-state-in-effect on the
  categories hook, deliberately left as-is in Phase C — it's the
  "init from late-arriving async data" pattern; baseline matches).
- yarn tsc: clean.

Migration path (per docs/ARCHITECTURE.md)
- This is the smallest possible Zustand pilot (~30 lines), chosen
  because the let-singleton anti-pattern was the most obvious quick
  win and the React Compiler was already complaining about it.
- Next adoption targets (cross-feature UI state): the toolbar's
  active-window state (currently inside scattered Contexts), the
  notification center's open-state, the catalog's currentPage/selection
  state (after the god-hook split).

https://claude.ai/code/session_01GrR87LAqnAEyKG2ZbmQt5Q

package.json

@@ -29,7 +29,8 @@
         "react-error-boundary": "^6.1.1",
         "react-icons": "^5.6.0",
         "react-player": "^2.16.0",
-        "use-between": "^1.4.0"
+        "use-between": "^1.4.0",
+        "zustand": "^5.0.13"
     },
     "devDependencies": {
         "@tailwindcss/forms": "^0.5.11",

src/components/navigator/views/NavigatorRoomCreatorView.tsx

@@ -5,13 +5,11 @@ import { GetClubMemberLevel, GetConfigurationValue, IRoomModel, LocalizeText, Se
 import { Button, Flex, Grid, LayoutCurrencyIcon, LayoutGridItem, Text } from '../../../common';
 import { useNavigator } from '../../../hooks';
 import { NitroInput } from '../../../layout';
-
-let isCreatingRoom = false;
-let createRoomTimeout: ReturnType<typeof setTimeout> = null;
+import { useRoomCreatorStore } from './navigatorRoomCreatorStore';
 
 const MAX_VISITORS_LIST: number[] = Array.from({ length: 10 }, (_, i) => (i + 1) * 10);
 
-export const NavigatorRoomCreatorView: FC<{}> = props =>
+export const NavigatorRoomCreatorView: FC = () =>
 {
     const [ name, setName ] = useState<string>(null);
     const [ description, setDescription ] = useState<string>(null);
@@ -25,7 +23,8 @@ export const NavigatorRoomCreatorView: FC<{}> = props =>
 
         return (models && models.length) ? models[0].name : '';
     });
-    const [ isCreating, setIsCreating ] = useState<boolean>(isCreatingRoom);
+    const isCreating = useRoomCreatorStore(s => s.isCreating);
+    const beginCreate = useRoomCreatorStore(s => s.beginCreate);
     const { categories = null } = useNavigator();
 
     const hcDisabled = GetConfigurationValue<boolean>('hc.disabled', false);
@@ -41,19 +40,11 @@ export const NavigatorRoomCreatorView: FC<{}> = props =>
 
     const createRoom = () =>
     {
-        if(isCreatingRoom) return;
+        if(useRoomCreatorStore.getState().isCreating) return;
 
-        isCreatingRoom = true;
-        setIsCreating(true);
+        beginCreate();
 
         SendMessageComposer(new CreateFlatMessageComposer(name, description, 'model_' + selectedModelName, Number(category), Number(visitorsCount), tradesSetting));
-
-        if(createRoomTimeout) clearTimeout(createRoomTimeout);
-        createRoomTimeout = setTimeout(() =>
-        {
-            isCreatingRoom = false;
-            setIsCreating(false);
-        }, 5000);
     };
 
     useEffect(() =>

src/components/navigator/views/navigatorRoomCreatorStore.ts

@@ -0,0 +1,44 @@
+import { createNitroStore } from '../../../state/createNitroStore';
+
+const CREATE_LOCKOUT_MS = 5000;
+
+interface RoomCreatorState
+{
+    isCreating: boolean;
+    /**
+     * Latch `isCreating` to true and auto-clear after CREATE_LOCKOUT_MS.
+     * Acts as a debounce so duplicate clicks on the Create button can't
+     * dispatch the composer twice.
+     */
+    beginCreate: () => void;
+}
+
+/**
+ * Replaces the previous `let isCreatingRoom` / `let createRoomTimeout`
+ * module-level pair (anti-pattern flagged by the React Compiler:
+ * "Writing to a variable defined outside a component or hook").
+ *
+ * The timer handle lives in the store's closure so a remount of the
+ * view doesn't reset the in-flight lockout, and so React strict-mode's
+ * double-mount no longer schedules two pending timers.
+ */
+export const useRoomCreatorStore = createNitroStore<RoomCreatorState>()((set) =>
+{
+    let timeoutHandle: ReturnType<typeof setTimeout> | null = null;
+
+    return {
+        isCreating: false,
+        beginCreate: () =>
+        {
+            if(timeoutHandle !== null) clearTimeout(timeoutHandle);
+
+            set({ isCreating: true });
+
+            timeoutHandle = setTimeout(() =>
+            {
+                timeoutHandle = null;
+                set({ isCreating: false });
+            }, CREATE_LOCKOUT_MS);
+        }
+    };
+});

src/state/createNitroStore.ts

@@ -1,42 +1,15 @@
 /**
- * Skeleton for proposal #5 (unified UI store).
+ * Re-export of zustand's `create` under a project-local name.
  *
- * NOT YET ENABLED — `zustand` is not in package.json.
- * To activate:
+ * Convention: each domain owns one store file. Either:
+ *   - `src/state/<domain>.ts` for cross-feature stores
+ *   - `src/components/<area>/<feature>Store.ts` for feature-local stores
  *
- *   yarn add zustand
+ * Components subscribe to specific slices only:
  *
- * Then this file becomes:
+ *   const isCreating = useNavigatorRoomCreatorStore(s => s.isCreating);
  *
- *   import { create } from 'zustand';
- *   export const createNitroStore = create;
- *
- * The naming convention below documents the intended structure: each
- * feature owns one slice file under `src/features/<feature>/state/`,
- * importing `createNitroStore` from here.
- *
- * Example slice (to be created when zustand is installed):
- *
- *   // src/features/wired-tools/state/wiredToolsSlice.ts
- *   import { createNitroStore } from '../../../state/createNitroStore';
- *
- *   type WiredToolsState = {
- *       activeTab: 'monitor' | 'variables' | 'inspection' | 'chests' | 'settings';
- *       setActiveTab: (tab: WiredToolsState['activeTab']) => void;
- *   };
- *
- *   export const useWiredToolsStore = createNitroStore<WiredToolsState>()((set) => ({
- *       activeTab: 'monitor',
- *       setActiveTab: (tab) => set({ activeTab: tab }),
- *   }));
- *
- * First migration target suggested in docs/ARCHITECTURE.md is the
- * `let isCreatingRoom = false` / `createRoomTimeout` singleton pair in
- * NavigatorRoomCreatorView.tsx — a ~5-line conversion that removes a
- * react-compiler/react-compiler "writing outside component" violation.
+ * Do NOT pull the whole store (`const all = useStore()`) — that
+ * subscribes to every change and defeats the point.
  */
-
-export const createNitroStore = (): never =>
-{
-    throw new Error('createNitroStore is not enabled. See docs/ARCHITECTURE.md proposal #5.');
-};
+export { create as createNitroStore } from 'zustand';

yarn.lock

@@ -3221,3 +3221,8 @@ zod@^3.22.4:
   version "4.4.3"
   resolved "https://registry.yarnpkg.com/zod/-/zod-4.4.3.tgz#b680f172885d18bbebf21a834ea25e55a1bbf356"
   integrity sha512-ytENFjIJFl2UwYglde2jchW2Hwm4GJFLDiSXWdTrJQBIN9Fcyp7n4DhxJEiWNAJMV1/BqWfW/kkg71UDcHJyTQ==
+
+zustand@^5.0.13:
+  version "5.0.13"
+  resolved "https://registry.yarnpkg.com/zustand/-/zustand-5.0.13.tgz#06995c126e8903cd27100af04da91c36ae3051ed"
+  integrity sha512-efI2tVaVQPqtOh114loML/Z80Y4NP3yc+Ff0fYiZJPauNeWZeIp/bRFD7I9bfmCOYBh/PHxlglQ9+wvlwnPikQ==