Add ghost CPUs with original Pac-Man AI targeting

Implement four ghosts (Blinky, Pinky, Inky, Clyde) with authentic
Pac-Man AI: Blinky chases directly, Pinky targets 2 tiles ahead
(with original up-direction bug), Inky uses vector doubling from
Blinky, Clyde switches to scatter within 8-tile radius.

Includes chase/scatter mode cycling, ghost house exit with staggered
delays, directional sprite rendering with animation, and ghost-pacman
collision detection.

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

pacman-project/tests/all-tests.rkt

@@ -11,6 +11,7 @@
         (prefix (pacman-project tests test-position) position:)
         (prefix (pacman-project tests test-maze) maze:)
         (prefix (pacman-project tests test-pacman) pacman:)
+        (prefix (pacman-project tests test-ghost) ghost:)
         (prefix (pacman-project tests test-score) score:)
         (prefix (pacman-project tests test-timer) timer:))
 
@@ -18,6 +19,7 @@
   (position:test)
   (maze:test)
   (pacman:test)
+  (ghost:test)
   (score:test)
   (timer:test))