feat(content): demo the state engine (generator unlocks/lights the cellar)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Semesterprojekt/src/main/resources/world/items.yaml

@@ -22,3 +22,15 @@
   id: key
   name: Brass Key
   description: A small brass key, polished from use.
+
+- type: switchable
+  id: generator
+  name: Generator
+  description: A rusty generator with a heavy lever.
+  initialState: false
+  onText: |
+    You heave the lever. Somewhere deep in the manor, the lights flicker on.
+  offText: |
+    You pull the lever back; the manor falls dark again.
+  effects:
+    - { setFlag: power_on }