fix: prevent avatar fly-in and hide local player's own hover

Two critical UX fixes for hover avatars:

1. PREVENT FLY-IN FROM TOP-LEFT:
   - Initialize position state as null instead of {x:0, y:0}
   - Don't render avatar until position is calculated from card element
   - Set immediate:true on first render to prevent animation
   - Add opacity spring (0→1) for smooth fade-in
   - Result: Avatar appears exactly where it should, no fly-in animation

2. HIDE YOUR OWN HOVER AVATAR:
   - Filter out local player (isLocal === true) from hover avatar rendering
   - Only show remote players' hover avatars
   - You see opponents hovering, but not your own cursor
   - Result: Cleaner UX, less visual noise on your own session

BEFORE:
- Avatar would fly in from (0,0) top-left corner when first hovering
- You'd see your own avatar following your mouse (distracting)

AFTER:
- Avatar appears smoothly at the correct card position
- Only remote players' avatars are visible
- Feels like watching someone else's cursor, not your own

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

apps/web/src/app/arcade/matching/components/MemoryGrid.tsx

@@ -92,7 +92,7 @@ function HoverAvatar({
   playerInfo: { emoji: string; name: string; color?: string }
   cardElement: HTMLElement | null
 }) {
-  const [position, setPosition] = useState({ x: 0, y: 0 })
+  const [position, setPosition] = useState<{ x: number; y: number } | null>(null)
 
   // Update position when card element changes
   useEffect(() => {
@@ -106,22 +106,29 @@ function HoverAvatar({
   }, [cardElement])
 
   // Smooth spring animation for position changes
+  // Only animate if we have a position (prevents fly-in from 0,0)
   const springProps = useSpring({
-    x: position.x,
-    y: position.y,
+    x: position?.x ?? 0,
+    y: position?.y ?? 0,
+    opacity: position ? 1 : 0, // Fade in when position is set
     config: {
       tension: 280,
       friction: 60,
       mass: 1,
     },
+    immediate: !position, // No animation on first render
   })
 
+  // Don't render until we have a position
+  if (!position) return null
+
   return (
     <animated.div
       style={{
         position: 'fixed',
         left: springProps.x,
         top: springProps.y,
+        opacity: springProps.opacity, // Fade in smoothly
         width: '48px',
         height: '48px',
         borderRadius: '50%',
@@ -363,6 +370,11 @@ export function MemoryGrid() {
       {state.playerHovers &&
         Object.entries(state.playerHovers)
           .filter(([_, cardId]) => cardId !== null) // Only show if hovering a card
+          .filter(([playerId]) => {
+            // Don't show your own hover avatar (only show remote players)
+            const player = playerMap.get(playerId)
+            return player?.isLocal !== true
+          })
           .map(([playerId, cardId]) => {
             const playerInfo = getPlayerHoverInfo(playerId)
             const cardElement = cardId ? cardRefs.current.get(cardId) : null