feat(cmat): add cmake build for course material

Add a CMakeLists.txt to each exercise directory, included from
cmat/CMakeLists.txt, so every exercise and solution becomes a buildable
target. GUI exercises link the curses-based DOS_Unix implementations on
Unix-like systems; the Windows-specific DOS variants are not compiled.
Exercises without a portable path or with missing dependencies (Boost)
are reported as not available at configure time.

Targets are excluded from the default build and built by name, e.g.
`cmake --build build --target Ex11`, so intentionally buggy exercises
such as Ex21 do not break the default build.

Also fix two portability issues: rename Ex11bug/pole.h to Pole.h for
case-sensitive filesystems and drop the extra Light:: qualification in
SolutionEx71A/Light.h. Document build commands and layout in AGENTS.md.

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

cmat/SolutionEx62Bonus/Main.cpp

@@ -0,0 +1,77 @@
+
+
+#include "Employee.h"
+#include "Person.h"
+#include <algorithm>
+#include <cctype>
+#include <iostream>
+#include <list>
+
+// header for file streams
+#include <fstream>
+// include headers that implement a archive in simple text format
+#include <boost/archive/text_iarchive.hpp>
+#include <boost/archive/text_oarchive.hpp>
+// include header that allows serialization of STL list
+#include <boost/serialization/export.hpp>
+#include <boost/serialization/list.hpp>
+BOOST_CLASS_EXPORT_GUID(Employee, "Employee")
+
+// STL collection of Person*
+std::list<Person *> people;
+
+void add(Person *newP) {
+    // creates a person, collects the information, adds person to list
+    newP->askForInfo();
+    people.push_back(newP);
+}
+
+void showPerson(Person *p) {
+    // displays a person
+    p->display();
+}
+
+void display() {
+    // displays all the people
+    std::for_each(people.begin(), people.end(), &showPerson);
+}
+
+int main() {
+    // deserialize existing file (if there is one)
+    try {
+        // create and open an archive for input
+        std::ifstream ifs("file.dat");
+        boost::archive::text_iarchive ia(ifs);
+        // read class state from archive
+        ia >> people;
+        // archive and stream closed when destructors are called
+    } catch (...) {
+    }
+
+    char choice = 0;
+
+    while (choice != 'X') {
+        switch (choice) {
+        case 'P':
+            add(new Person());
+            break;
+        case 'E':
+            add(new Employee());
+            break;
+        case 'D':
+            display();
+            break;
+        }
+        std::cout << "Enter choice: Add [P]erson, add [E]mployee, [D]isplay, e[X]it: ";
+        std::cin >> choice;
+        choice = std::toupper(choice);
+    }
+
+    // save data to archive
+    std::ofstream ofs("file.dat");
+    boost::archive::text_oarchive oa(ofs);
+    oa << people;
+    // archive and stream closed when destructors are called
+
+    return 0;
+}