Fix(Animation): Drive Pac-Man mouth animation from game loop, not draw callback

The draw callback receives no delta-time, so animation was stuck at 0.
Split draw-pacman! into draw (position/rotation) and animate-pacman!
(sprite sequence advancement). Animation is now called from the game
loop which has the real delta-time.

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

pacman-project/adt/game.rkt

@@ -28,9 +28,10 @@
             ((level 'key-press!) key)))
 
         ;; game-loop :: number -> /
-        ;; Called each frame for game state updates.
+        ;; Called each frame for game state updates and animation.
         (define (game-loop delta-time)
-          ((level 'update!) delta-time))
+          ((level 'update!) delta-time)
+          ((draw 'animate-pacman!) delta-time))
 
         ;; start! :: -> /
         ;; Starts the game by registering all callbacks.