Add tutorial READMEs and fix tutorial return codes

Add README.md files for moeo/tutorial/Lesson{1-4}, smp/tutorial/Lesson{1-4},
and mo/tutorial/Lesson9 — these tutorials had no documentation.

Fix return 1 → return 0 in 28 tutorial main() functions across mo/ and
smp/ that unconditionally returned failure status.

smp/tutorial/Lesson2/README.md

@@ -0,0 +1,30 @@
+# Homogeneous island model
+
+Three islands running the same algorithm (`eoEasyEA`) with a complete
+topology — all islands exchange individuals with all others.
+
+Same QAP problem as Lesson 1.
+
+## Running
+
+From the `build/smp/tutorial/Lesson2` directory:
+
+```shell
+./lesson2_homogeneous
+```
+
+The problem instance is loaded from `../lessonData.dat`.
+
+## How it works
+
+All islands share the same operators (evaluation, selection, crossover,
+mutation, replacement) but can have different parameters. The topology
+and island model are set up with:
+
+```c++
+Topology<Complete> topo;
+IslandModel<Indi> model(topo);
+```
+
+Each island gets its own population and generation limit, then the model
+runs them in parallel and handles migration.