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))
 

pacman-project/tests/test-ghost.rkt

@@ -0,0 +1,97 @@
+#lang r7rs
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;;                           Tests: Ghost ADT                                ;;
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+(define-library (pacman-project tests test-ghost)
+  (import (scheme base)
+          (pp1 tests)
+          (pacman-project adt ghost))
+  (export test)
+
+  (begin
+
+    ;; Test creation and initial state
+    (define (test-creation)
+      (define g (make-ghost 'blinky 11 14 0 27 0))
+      (define pos (g 'position))
+      (check-eq? (pos 'row) 11 "Start row should be 11")
+      (check-eq? (pos 'col) 14 "Start col should be 14")
+      (check-eq? (g 'type) 'blinky "Type should be blinky")
+      (check-eq? (g 'direction) 'left "Default direction should be left"))
+
+    ;; Test that exit-delay 0 means ghost starts outside (scatter mode)
+    (define (test-blinky-starts-active)
+      (define g (make-ghost 'blinky 11 14 0 27 0))
+      (check-eq? (g 'in-house?) #f "Blinky should start outside")
+      (check-eq? (g 'mode) 'scatter "Blinky should start in scatter"))
+
+    ;; Test that non-zero exit-delay means ghost starts in house
+    (define (test-pinky-starts-in-house)
+      (define g (make-ghost 'pinky 14 13 0 0 2000))
+      (check-eq? (g 'in-house?) #t "Pinky should start in house")
+      (check-eq? (g 'mode) 'in-house "Pinky mode should be in-house"))
+
+    ;; Test direction change
+    (define (test-direction)
+      (define g (make-ghost 'blinky 11 14 0 27 0))
+      ((g 'direction!) 'right)
+      (check-eq? (g 'direction) 'right "Direction should be right"))
+
+    ;; Test mode change and reverse queuing
+    (define (test-mode-change-queues-reverse)
+      (define g (make-ghost 'blinky 11 14 0 27 0))
+      ((g 'mode!) 'chase)
+      (check-eq? (g 'mode) 'chase "Mode should be chase")
+      (check-eq? ((g 'consume-reverse!)) #t "Reverse should be queued after mode change"))
+
+    ;; Test reverse consumed only once
+    (define (test-consume-reverse-once)
+      (define g (make-ghost 'blinky 11 14 0 27 0))
+      ((g 'mode!) 'chase)
+      ((g 'consume-reverse!))
+      (check-eq? ((g 'consume-reverse!)) #f "Reverse should be consumed after first call"))
+
+    ;; Test move
+    (define (test-move)
+      (define g (make-ghost 'blinky 11 14 0 27 0))
+      ((g 'move!) 0 -1)
+      (define pos (g 'position))
+      (check-eq? (pos 'col) 13 "Col should be 13 after move left"))
+
+    ;; Test scatter target
+    (define (test-scatter-target)
+      (define g (make-ghost 'blinky 11 14 0 27 0))
+      (define st (g 'scatter-target))
+      (check-eq? (st 'row) 0 "Scatter target row should be 0")
+      (check-eq? (st 'col) 27 "Scatter target col should be 27"))
+
+    ;; Test house timer expiry
+    (define (test-house-exit)
+      (define g (make-ghost 'pinky 14 13 0 0 2000))
+      ((g 'update-house-timer!) 1000)
+      (check-eq? (g 'in-house?) #t "Still in house after 1000ms")
+      ((g 'update-house-timer!) 1000)
+      (check-eq? (g 'in-house?) #f "Should exit house after 2000ms")
+      (check-eq? (g 'mode) 'scatter "Should be in scatter after exiting"))
+
+    ;; Test movement timer
+    (define (test-movement-timer)
+      (define g (make-ghost 'blinky 11 14 0 27 0))
+      (check-eq? ((g 'advance-movement-timer!) 100) 100 "Timer should be 100")
+      (check-eq? ((g 'advance-movement-timer!) 120) 220 "Timer should be 220")
+      ((g 'reset-movement-timer!))
+      (check-eq? (g 'movement-timer) 0 "Timer should reset to 0"))
+
+    (define (test)
+      (run-test test-creation "Ghost: creation and initial state")
+      (run-test test-blinky-starts-active "Ghost: Blinky starts active")
+      (run-test test-pinky-starts-in-house "Ghost: Pinky starts in house")
+      (run-test test-direction "Ghost: direction change")
+      (run-test test-mode-change-queues-reverse "Ghost: mode change queues reverse")
+      (run-test test-consume-reverse-once "Ghost: consume reverse only once")
+      (run-test test-move "Ghost: move")
+      (run-test test-scatter-target "Ghost: scatter target")
+      (run-test test-house-exit "Ghost: house timer exit")
+      (run-test test-movement-timer "Ghost: movement timer"))))