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/Lesson3/README.md

@@ -0,0 +1,27 @@
+# Heterogeneous island model
+
+Two islands running different algorithms: an `eoEasyEA` on the QAP problem
+and a PSO on a bitstring problem, connected via conversion functions.
+
+## Running
+
+From the `build/smp/tutorial/Lesson3` directory:
+
+```shell
+./lesson3_heterogeneous
+```
+
+## How it works
+
+When islands use different representations, you need conversion functions
+to translate individuals during migration. In this example, `fromBase()`
+and `toBase()` convert between the QAP permutation and the PSO bitstring:
+
+```c++
+Indi2 fromBase(Indi& i, unsigned size) { ... }
+Indi toBase(Indi2& i) { ... }
+```
+
+The conversions here are dummy placeholders (they just create random
+individuals), but in a real application you would implement meaningful
+mappings between representations.