fix(spatial-office#12): show agent name labels only on hover

Per design-critique-1 Issue 3 (P1), agent name labels were always
visible and stacked into unreadable text when agents were near
each other. Now matches Stardew Valley convention: name shows
on hover only.

Single conditional change. The hover tooltip (Html overlay with
status + current task) is unchanged.

packages/frontend/src/AgentSprite.jsx

@@ -132,7 +132,8 @@ export default function AgentSprite({ agent, hovered, onHover }) {
         />
       </mesh>
 
-      {/* Agent name label */}
+      {/* Agent name label — hover only (per design-critique-1 Issue 3, P1) */}
+      {hovered && (
         <Text
           position={
             targetPos
@@ -148,6 +149,7 @@ export default function AgentSprite({ agent, hovered, onHover }) {
         >
           {agent.name}
         </Text>
+      )}
 
       {/* Hover tooltip */}
       {hovered && (