feat(navigator): empty-state + skeleton views, fix double search fetch (P4 wave 1a)

Visual polish, first wave:
- NavigatorEmptyStateView: replaces the bare "No rooms found" text with a
  centered icon + message + a Create-room CTA. Reuses existing i18n keys
  (navigator.search.returned.no.results / .roomsettings.moderation.none /
  .createroom.create) so no new localization entries are needed.
- NavigatorSearchSkeletonView: animate-pulse placeholder rows shown while a
  search is in flight and no result is cached yet (matches the HK dashboard
  skeleton pattern). Replaces the NitroCard.Content spinner overlay for the
  result list.

Bug fix bundled in: NavigatorSearchView called useNavigatorSearch() a second
time purely to read searchResult for its input-sync effect. Since the hook is
not a useBetween singleton, that registered a duplicate NavigatorSearchEvent
listener AND fired a duplicate NavigatorSearchComposer on every search.
NavigatorView now owns the single useNavigatorSearch() call and passes
searchResult to NavigatorSearchView via prop.

Test maintenance: useNavigatorSearch.test.tsx was written for the original
useNitroQuery implementation, which upstream reverted (05d71dd1) to
useMessageEvent + useState. Removed the dead QueryClient scaffolding, fixed
case 1 (assert no fetch starts with empty tab), dropped case 7 (the query
invalidator no longer exists). 6 cases, all green.

Full suite 471/471. Typecheck: only the environmental renderer-mismatch
errors (soundboard / rare-values / floorplan APIs absent from the linked
renderer), none in navigator files.

src/components/navigator/NavigatorView.tsx

@@ -14,8 +14,10 @@ import { NavigatorRoomCreatorView } from './views/NavigatorRoomCreatorView';
 import { NavigatorRoomInfoView } from './views/NavigatorRoomInfoView';
 import { NavigatorRoomLinkView } from './views/NavigatorRoomLinkView';
 import { NavigatorRoomSettingsView } from './views/room-settings/NavigatorRoomSettingsView';
+import { NavigatorEmptyStateView } from './views/search/NavigatorEmptyStateView';
 import { NavigatorSearchResultView } from './views/search/NavigatorSearchResultView';
 import { NavigatorSearchSavesResultView } from './views/search/NavigatorSearchSavesResultView';
+import { NavigatorSearchSkeletonView } from './views/search/NavigatorSearchSkeletonView';
 import { NavigatorSearchView } from './views/search/NavigatorSearchView';
 
 export const NavigatorView: FC<{}> = props =>
@@ -132,7 +134,7 @@ export const NavigatorView: FC<{}> = props =>
                             <FaPlus className="fa-icon" />
                         </NitroCard.TabItem>
                     </NitroCard.Tabs>
-                    <NitroCard.Content isLoading={ isFetching }>
+                    <NitroCard.Content>
                         { !isCreatorOpen &&
                             <div className="flex h-full overflow-hidden gap-2">
                                 { isOpenSavesSearches &&
@@ -140,13 +142,13 @@ export const NavigatorView: FC<{}> = props =>
                                         <NavigatorSearchSavesResultView searches={ navigatorSearches || [] } />
                                     </div> }
                                 <div className="flex flex-col w-full overflow-hidden gap-2">
-                                    <NavigatorSearchView />
+                                    <NavigatorSearchView searchResult={ searchResult } />
                                     <div ref={ elementRef } className="flex flex-col flex-1 min-h-0 overflow-auto gap-2">
+                                        { (isFetching && !searchResult) &&
+                                            <NavigatorSearchSkeletonView /> }
                                         { searchResult && searchResult.results.map((result, index) => <NavigatorSearchResultView key={ index } searchResult={ result } />) }
                                         { searchResult && (!searchResult.results || searchResult.results.length === 0) &&
-                                            <div className="nitro-card-panel px-3 py-2 text-sm text-muted">
-                                                { LocalizeText(searchResult.code === 'myworld_view' ? 'navigator.roomsettings.moderation.none' : 'navigator.search.returned.no.results') }
-                                            </div> }
+                                            <NavigatorEmptyStateView code={ searchResult.code } onCreateRoom={ () => useNavigatorUiStore.getState().openCreator() } /> }
                                     </div>
                                     <Flex className="nitro-card-divider pt-2 border-t gap-2">
                                         <Flex pointer alignItems="center" justifyContent="center"

src/components/navigator/views/search/NavigatorEmptyStateView.tsx

@@ -0,0 +1,33 @@
+import { FC } from 'react';
+import { FaPlus, FaSearch } from 'react-icons/fa';
+import { LocalizeText } from '../../../../api';
+import { Button } from '../../../../common';
+
+interface NavigatorEmptyStateViewProps
+{
+    code: string;
+    onCreateRoom: () => void;
+}
+
+export const NavigatorEmptyStateView: FC<NavigatorEmptyStateViewProps> = props =>
+{
+    const { code, onCreateRoom } = props;
+
+    const isMyWorld = (code === 'myworld_view');
+    const messageKey = isMyWorld ? 'navigator.roomsettings.moderation.none' : 'navigator.search.returned.no.results';
+
+    return (
+        <div className="flex flex-1 flex-col items-center justify-center gap-3 px-4 py-8 text-center">
+            <div className="flex h-16 w-16 items-center justify-center rounded-full bg-black/5 text-muted">
+                <FaSearch size={ 26 } className="opacity-40" />
+            </div>
+            <div className="text-sm text-muted max-w-[240px]">
+                { LocalizeText(messageKey) }
+            </div>
+            <Button variant="primary" onClick={ onCreateRoom }>
+                <FaPlus className="fa-icon me-1" />
+                { LocalizeText('navigator.createroom.create') }
+            </Button>
+        </div>
+    );
+};

src/components/navigator/views/search/NavigatorSearchSkeletonView.tsx

@@ -0,0 +1,25 @@
+import { FC } from 'react';
+
+interface NavigatorSearchSkeletonViewProps
+{
+    rows?: number;
+}
+
+export const NavigatorSearchSkeletonView: FC<NavigatorSearchSkeletonViewProps> = props =>
+{
+    const { rows = 5 } = props;
+
+    return (
+        <div className="flex flex-col gap-2" aria-hidden="true">
+            { Array.from({ length: rows }).map((_, index) =>
+                <div key={ index } className="nitro-card-panel flex items-center gap-2 px-2 py-2">
+                    <div className="h-10 w-10 shrink-0 rounded bg-black/10 animate-pulse" />
+                    <div className="flex flex-1 flex-col gap-1">
+                        <div className="h-3 w-1/2 rounded bg-black/10 animate-pulse" />
+                        <div className="h-2.5 w-1/3 rounded bg-black/10 animate-pulse" />
+                    </div>
+                    <div className="h-4 w-8 shrink-0 rounded bg-black/10 animate-pulse" />
+                </div>) }
+        </div>
+    );
+};

src/components/navigator/views/search/NavigatorSearchView.tsx

@@ -1,15 +1,21 @@
+import { NavigatorSearchResultSet } from '@nitrots/nitro-renderer';
 import { FC, KeyboardEvent, useEffect, useState } from 'react';
 import { FaSearch } from 'react-icons/fa';
 import { INavigatorSearchFilter, LocalizeText, SearchFilterOptions } from '../../../../api';
 import { Button } from '../../../../common';
-import { useNavigatorData, useNavigatorSearch, useNavigatorUiStore } from '../../../../hooks';
+import { useNavigatorData, useNavigatorUiStore } from '../../../../hooks';
 
-export const NavigatorSearchView: FC<{}> = props =>
+interface NavigatorSearchViewProps
 {
+    searchResult: NavigatorSearchResultSet | null;
+}
+
+export const NavigatorSearchView: FC<NavigatorSearchViewProps> = props =>
+{
+    const { searchResult } = props;
     const [ searchFilterIndex, setSearchFilterIndex ] = useState(0);
     const [ inputText, setInputText ] = useState('');
     const { topLevelContext } = useNavigatorData();
-    const { searchResult } = useNavigatorSearch();
 
     // Sync the input text display when a server result arrives (e.g. on tab switch
     // or deep-link navigation that sets the filter through the store directly).