fix(bug,perf): poll first-vote race, stale timeline ref, lazy GifPicker/EmojiBoard, focusItem timer leak, RoomNavItem memo

BUG-18: clearTimeout cleanup in focusItem useLayoutEffect prevents leaked timers
BUG-24: Room timeline listener catches first poll vote before Relations object exists
BUG-25: Use timelineRef.current in handleOpenEvent to prevent stale index on rapid navigation
Perf-6: React.lazy + Suspense for GifPicker and EmojiBoard (initial bundle -114 kB)
Perf-7: React.memo on RoomNavItem to prevent re-renders on unrelated state

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/app/features/room/RoomInput.tsx

@@ -30,7 +30,7 @@ import {
 } from 'folds';
 
 import { useMatrixClient } from '../../hooks/useMatrixClient';
-import { GifPicker } from '../../components/GifPicker';
+const GifPicker = React.lazy(() => import('../../components/GifPicker').then((m) => ({ default: m.GifPicker })));
 import { useClientConfig } from '../../hooks/useClientConfig';
 import {
   CustomEditor,
@@ -56,7 +56,8 @@ import {
   trimCommand,
   getMentions,
 } from '../../components/editor';
-import { EmojiBoard, EmojiBoardTab } from '../../components/emoji-board';
+import { EmojiBoardTab } from '../../components/emoji-board/types';
+const EmojiBoard = React.lazy(() => import('../../components/emoji-board').then((m) => ({ default: m.EmojiBoard })));
 import { UseStateProvider } from '../../components/UseStateProvider';
 import {
   TUploadContent,
@@ -690,7 +691,7 @@ export const RoomInput = forwardRef<HTMLDivElement, RoomInputProps>(
                         : emojiBtnRef.current?.getBoundingClientRect() ?? undefined
                     }
                     content={
-                      <EmojiBoard
+                      <React.Suspense fallback={null}><EmojiBoard
                         tab={emojiBoardTab}
                         onTabChange={setEmojiBoardTab}
                         imagePackRooms={imagePackRooms}
@@ -707,7 +708,7 @@ export const RoomInput = forwardRef<HTMLDivElement, RoomInputProps>(
                             return t;
                           });
                         }}
-                      />
+                      /></React.Suspense>
                     }
                   >
                     {!hideStickerBtn && (
@@ -758,11 +759,11 @@ export const RoomInput = forwardRef<HTMLDivElement, RoomInputProps>(
                           : undefined
                       }
                       content={
-                        <GifPicker
+                        <React.Suspense fallback={null}><GifPicker
                           apiKey={gifApiKey}
                           onSelect={handleGifSelect}
                           requestClose={() => setGifOpen(false)}
-                        />
+                        /></React.Suspense>
                       }
                     >
                       <IconButton