fix: use correct Datastar keydown event syntax

Replace invalid .key_enter and .enter modifiers with evt.key === 'Enter'
guard in the expression, per Datastar docs. Also fix __stop and __throttle
modifier syntax to use double underscores.

features/snakegame/pages/game.templ

@@ -34,7 +34,7 @@ templ GamePage(sg *snake.SnakeGame, mySlot int, messages []chat.Message, chatCfg
 			class="snake-wrapper flex flex-col items-center gap-4 p-4"
 			data-signals={ `{"chatMsg":""}` }
 			data-init={ datastar.GetSSE("/snake/%s/events", gameID) }
-			data-on:keydown.throttle_100ms={ keydownScript(gameID) }
+			data-on:keydown__throttle.100ms={ keydownScript(gameID) }
 			tabindex="0"
 		>
 			@GameContent(sg, mySlot, messages, chatCfg, gameID)