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.

mo/tutorial/Lesson9/README.md

@@ -0,0 +1,48 @@
+# Variable Neighborhood Search (VNS)
+
+VNS on the N-Queens problem, using multiple neighborhood structures to
+escape local optima.
+
+The N-Queens problem places N queens on an N x N chessboard so that no two
+queens attack each other. The representation is a permutation (one queen
+per column) and the fitness counts conflicts (minimized).
+
+## Running
+
+From the `build/mo/tutorial/Lesson9` directory:
+
+```shell
+./VNS -V=12
+```
+
+This runs VNS on a 12-queens instance with a 3-second time limit.
+
+## How it works
+
+VNS alternates between perturbation (shaking) and local search using
+different neighborhood structures. Here, two neighborhoods are used:
+
+```c++
+shiftNeighborhood shiftNH((vecSize-1) * (vecSize-1));
+swapNeighborhood swapNH(vecSize * (vecSize-1) / 2);
+```
+
+Each has its own hill-climber and mutation operator:
+
+```c++
+moSimpleHC<shiftNeighbor> ls1(shiftNH, fullEval, shiftEval);
+moSimpleHC<swapNeighbor> ls2(swapNH, fullEval, swapEval);
+
+moRndVectorVNSelection<Queen> selectNH(ls1, shiftMut, true);
+selectNH.add(ls2, swapMut);
+```
+
+`moRndVectorVNSelection` randomly picks which neighborhood/local search
+to apply at each iteration. Forward (`moForwardVectorVNSelection`) and
+backward (`moBackwardVectorVNSelection`) selection strategies are also
+available. The search runs until the `moTimeContinuator` time limit:
+
+```c++
+moTimeContinuator<shiftNeighbor> cont(3);  // 3 seconds
+moVNS<shiftNeighbor> vns(selectNH, acceptCrit, fullEval, cont);
+```

mo/tutorial/Lesson9/VNS.cpp

@@ -284,5 +284,5 @@ int main(int argc, char **argv)
     catch (exception& e) {
         cout << "Exception: " << e.what() << '\n';
     }
-    return 1;
+    return 0;
 }