feat(cmat): pass hints to Ex42 observers

Extend the Ex42 observer pattern with Hint objects so each
observer receives the reason for the update instead of
querying the subject:

- Subject::notify() and Observer::update() now take a
  const Hint& argument.
- Add LightHint and WaitHint carrying the traffic light
  state and WAIT button state, defined in Pelican.h.
- Pole dispatches on hint type using dynamic_cast.
- The Pole constructor sets its initial lights directly
  from the Pelican's current state, since no notification
  is sent at startup. Stopgap until the initial update
  is handled properly.

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

cmat/Ex42/Pole.h

@@ -1,28 +1,28 @@
-
-#ifndef POLE_H
-#define POLE_H
-
-#include "Light.h"
-#include "Observer.h"
-#include "Pelican.h"
-
-class Pole : public Observer {
-  public:
-    Pole(int x, int y, Pelican &p);
-    ~Pole();
-
-    void setTrafficLights(Pelican::PelicanState state);
-    void setWaitLight(bool pressed);
-
-    void update();
-
-  private:
-    Pelican &myPelican;
-
-    enum LightName { RED_LIGHT, YELLOW_LIGHT, GREEN_LIGHT, GREEN_MAN, RED_MAN };
-
-    Light *lights[RED_MAN + 1];
-    Light *waitLight;
-};
-
-#endif
+
+#ifndef POLE_H
+#define POLE_H
+
+#include "Light.h"
+#include "Observer.h"
+#include "Pelican.h"
+
+class Pole : public Observer {
+  public:
+    Pole(int x, int y, Pelican &p);
+    ~Pole();
+
+    void setTrafficLights(Pelican::PelicanState state);
+    void setWaitLight(bool pressed);
+
+    void update(const Hint& hint);
+
+  private:
+    Pelican &myPelican;
+
+    enum LightName { RED_LIGHT, YELLOW_LIGHT, GREEN_LIGHT, GREEN_MAN, RED_MAN };
+
+    Light *lights[RED_MAN + 1];
+    Light *waitLight;
+};
+
+#endif