feat(cmat): implement Ex41 observer pattern

Refactor the Pelican crossing exercise to use the Observer
pattern: Pelican acts as Subject and each Pole observes it,
replacing direct calls through the owned Pole pointer.

Co-authored-by: Qwen 3.8 27B <qwen3.8_27b-q3_k_xl@lmstudio.local>

cmat/Ex41/Pole.cpp

@@ -1,8 +1,9 @@
 #include "Pole.h"
 #include "Screen.h"
 
-Pole::Pole(int x, int y) : waitLight(new Light("WAIT", x + 6, y + 12, Screen::WHITE)) {
+Pole::Pole(int x, int y, Pelican& pelican) : waitLight(new Light("WAIT", x + 6, y + 12, Screen::WHITE)), pelican(pelican) {
     using namespace Screen; // we will discuss namespaces in the course
+    pelican.attach(this);
 
     lights[RED_LIGHT] = new Light("*", x + 11, y + 3, RED);
     lights[RED_MAN] = new Light("*<-=", x + 6, y + 4, RED);
@@ -57,3 +58,8 @@ void Pole::setTrafficLights(Pelican::PelicanState state) {
 }
 
 void Pole::setWaitLight(bool pressed) { waitLight->set(pressed ? Light::ON : Light::OFF); }
+
+void Pole::update() {
+    setTrafficLights(pelican.getState());
+    setWaitLight(pelican.isPressed());
+}