Add three C# demo examples for Slice with Lambda

- MetaphorFree.cs: guard -> SomeDependency.mightThrowWhenPreconditionNotSatisfied(a) -> tail,
  capture-to-parameter story for the deck
- WeatherStation.cs: SprinklerController, LightSensor.Read() byte -> SunExposure, tail branches
- IceCreamShop.cs: third repetition, Thermometer byte -> Warmth, tail branches

ideas/split-loop-with-lambda/exercise/csharp/WeatherStation.cs

@@ -0,0 +1,71 @@
+// Example 2 — Weather Station domain demo of Slice with Lambda (C#)
+//
+// Condensed mechanics: https://sammancoaching.org/refactorings/slice.html
+// (where that page says mock, we use a lambda instead).
+//
+// Cast (Head First Design Patterns Weather Station, reduced):
+//   LightSensor      — hardware-ish dependency. Read() returns a byte.
+//   SunExposure      — enum. Reading > 128 => Sunny, otherwise Shady.
+//   WateringDuration — enum. None / Medium / Short.
+//                      (Long is YAGNI until the for-loop version of this
+//                      exercise exists.)
+//   SprinklerController — the client. Owns the _wateredToday flag, so the
+//                      guard is about client state, not sensor state.
+
+using System;
+
+public enum SunExposure
+{
+    Shady,
+    Sunny
+}
+
+public enum WateringDuration
+{
+    None,
+    Medium,
+    Short
+}
+
+public class LightSensor
+{
+    private readonly Random _rng = new Random();    // stand-in for hardware noise
+
+    public byte Read()
+    {
+        return (byte)_rng.Next(256);
+    }
+}
+
+public class SprinklerController
+{
+    private readonly LightSensor _lightSensor;
+    private bool _wateredToday;                     // event-style client state
+
+    public SprinklerController(LightSensor lightSensor)
+    {
+        _lightSensor = lightSensor;
+    }
+
+    public WateringDuration ScheduleWatering()
+    {
+        if (_wateredToday)                          // guard: client state, stays
+        {
+            return WateringDuration.None;
+        }
+
+        _wateredToday = true;                       // set only after watering
+        byte reading = _lightSensor.Read();         // middle: unwanted dependency
+        SunExposure exposure = ToSunExposure(reading);
+        if (exposure == SunExposure.Sunny)          // tail: complex behaviour below
+        {                                           // the extraction point
+            return WateringDuration.Medium;
+        }
+        return WateringDuration.Short;
+    }
+
+    private static SunExposure ToSunExposure(byte reading)
+    {
+        return reading > 128 ? SunExposure.Sunny : SunExposure.Shady;
+    }
+}