feat(world): Haunted Manor content expansion (14 rooms, one world)

Replace the 5-room demo with a condensed 14-room manor on one spine
(restore power -> escape) that stacks all five mechanics, plus an optional
spirit thread feeding 3 prioritized endings (no hard-fail). Pure YAML on the
existing engines: 14 rooms across 3 levels, ~16 items, 5 combinations, the
old_man hint NPC, restore_power + lay_to_rest quests, and 3 endings.

Consolidate to one world: remove the toy "Test Manor" test fixture so the
loader tests exercise the real shipped world. Adapt WorldLoaderTest and
TutorialLoaderTest to form-invariants of the real world, and add
WorldSolvableTest, which walks the critical path (light/lock gating +
Combinations.tryUse + flags) to guarantee power_on, ghost_banished, and a
victory ending are reachable — an unsolvable world now fails the build.

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

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

@@ -1,57 +1,18 @@
-- type: readable
-  id: letter
-  name: Letter
-  description: A crumpled piece of paper.
-  readText: |
-    "Meet me at midnight in the cellar. - A."
+# Haunted Manor items. Two items — lit_torch and fuse — are intentionally left
+# unplaced: they exist only as the products of combinations. valve, generator
+# and shrine are scenery "fixtures": technically takeable, but written as fixed
+# in place; combinations resolve them from the room just as well as the bag.
+
+# ── Light sources ───────────────────────────────────────────────────────────
 
 - type: switchable
   id: lamp
   name: Oil Lamp
-  description: An old oil lamp, heavy with fuel.
+  description: An old oil lamp, heavy with fuel. Lighting it would push back the dark.
   initialState: false
   light: true
-  onText: The lamp flares to life, casting a warm glow.
-  offText: You snuff out the lamp.
-
-- type: plain
-  id: shovel
-  name: Shovel
-  description: A rusty shovel. Sturdy enough to dig.
-
-- type: plain
-  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 }
-
-- type: switchable
-  id: front_door
-  name: Front Door
-  description: The heavy front door. It would let you leave the manor for good.
-  initialState: false
-  onText: |
-    You haul the front door open and step out into the cold night.
-  offText: |
-    You ease the door shut again.
-  effects:
-    - { setFlag: fled }
-
-- type: plain
-  id: matches
-  name: Box of Matches
-  description: A small box of dry matches. They rattle when you shake it.
+  onText: The lamp flares to life, casting a warm, steady glow.
+  offText: You snuff out the lamp and the dark rushes back in.
 
 - type: plain
   id: torch
@@ -63,3 +24,101 @@
   name: Lit Torch
   description: A burning torch, throwing back the dark.
   light: true
+
+- type: plain
+  id: matches
+  name: Box of Matches
+  description: A small box of dry matches. They rattle when you shake it.
+
+# ── Power-restoration chain ──────────────────────────────────────────────────
+
+- type: plain
+  id: valve_wheel
+  name: Valve Wheel
+  description: A heavy iron wheel, sized to fit a drainage valve.
+
+- type: plain
+  id: valve
+  name: Drainage Valve
+  description: |
+    A rusted drainage valve set into the cellar wall. Its wheel is missing —
+    it is part of the house, not something you can carry off.
+
+- type: plain
+  id: fuse
+  name: Ceramic Fuse
+  description: A fat ceramic fuse, the kind that feeds a generator's main bus.
+
+- type: plain
+  id: generator
+  name: Generator
+  description: |
+    A rusty generator with an empty fuse socket. It is bolted to the floor —
+    you will have to work on it where it stands.
+
+# ── Spirit / relic chain ─────────────────────────────────────────────────────
+
+- type: plain
+  id: locket
+  name: Silver Locket
+  description: A tarnished silver locket. Something is engraved inside the clasp.
+
+- type: plain
+  id: photograph
+  name: Faded Photograph
+  description: A faded photograph of two figures standing before the manor.
+
+- type: plain
+  id: shrine
+  name: Stone Shrine
+  description: |
+    A small stone shrine with a shallow offering niche. It is mortared into
+    the chapel floor — a place to leave something, not to take it.
+
+# ── Exit ─────────────────────────────────────────────────────────────────────
+
+- type: switchable
+  id: front_door
+  name: Front Door
+  description: The heavy front door. It would let you leave the manor for good.
+  initialState: false
+  onText: |
+    You haul the front door open and step out into the cold night air.
+  offText: |
+    You ease the door shut again.
+  effects:
+    - { setFlag: left_manor }
+
+# ── Lore & flavour ───────────────────────────────────────────────────────────
+
+- type: readable
+  id: letter
+  name: Letter
+  description: A crumpled piece of paper, addressed to no one.
+  readText: |
+    "If you are reading this, the power has failed again. The fuse is in the
+    flooded cellar — drain it first. And whatever you hear upstairs at night:
+    it only wants to be remembered. — A."
+
+- type: readable
+  id: journal
+  name: Caretaker's Journal
+  description: A leather journal in a careful, anxious hand.
+  readText: |
+    "Day 9. The generator died and the cellar flooded the same week. I keep
+    the valve wheel in the conservatory now. Day 14. The chapel shrine takes
+    the locket — but it wants the photograph too, in that order, or nothing
+    happens at all."
+
+- type: readable
+  id: portrait
+  name: Family Portrait
+  description: A faded oil portrait above the dining-room hearth.
+  readText: |
+    A stern family poses before the manor. A small brass plate reads only:
+    "They never did leave."
+
+- type: plain
+  id: shovel
+  name: Shovel
+  description: A rusty shovel. Sturdy enough to dig, though nothing here needs digging.