semesterprojekt: implement full text adventure (phases 1-7)

Walking skeleton through Swing GUI: YAML-driven world (4 rooms,
4 items, 1 NPC), HashMap command dispatch with parser, three-tier
item hierarchy (readable / switchable / plain), and end-to-end
NPC give/receive flow. 67 tests green.

Semesterprojekt/src/test/resources/world/npcs.yaml

@@ -0,0 +1,10 @@
+- id: old_man
+  name: Old Man
+  description: stooped
+  greeting: |
+    greetings
+  reactions:
+    - onReceive: lamp
+      response: thanks
+      gives: key
+      consumes: lamp