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/main/resources/world/rooms.yaml

@@ -0,0 +1,41 @@
+- id: kitchen
+  name: Old Kitchen
+  description: |
+    A dusty kitchen. Cobwebs hang from the rafters
+    and a letter lies on the table.
+  exits:
+    north: hallway
+    east: cellar
+  items: [letter, lamp]
+  npcs: [old_man]
+
+- id: hallway
+  name: Dark Hallway
+  description: |
+    A long, dimly lit hallway. It smells musty.
+    Faint footsteps echo somewhere far away.
+  exits:
+    south: kitchen
+    west: library
+  items: []
+  npcs: []
+
+- id: library
+  name: Library
+  description: |
+    Tall shelves crammed with mouldering books.
+    An old chest stands in the corner.
+  exits:
+    east: hallway
+  items: [shovel]
+  npcs: []
+
+- id: cellar
+  name: Damp Cellar
+  description: |
+    Cold, damp, and very dark. You can barely
+    make out shapes against the far wall.
+  exits:
+    west: kitchen
+  items: []
+  npcs: []