feat: Character Creation user story — ADTs, properties, and Allium spec

- Level value object (1..10, level-capped health)
- Health value object (non-negative, pure sub/add)
- Status discriminated union (alive | dead)
- Character entity with private constructor and static factory
- 9 fast-check properties covering creation invariants
- Allium spec with entities, rules, and invariants

specs/character-creation.allium

@@ -0,0 +1,70 @@
+-- allium: 3
+
+-- allium: character-creation
+
+------------------------------------------------------------
+-- Value Types
+------------------------------------------------------------
+
+type Health {
+    value: Integer
+    requires: value >= 0
+}
+
+type Level {
+    value: Integer
+    requires: value >= 1 and value <= 10
+}
+
+type Status {
+    alive | dead
+}
+
+------------------------------------------------------------
+-- Entities
+------------------------------------------------------------
+
+entity Character {
+    name: String
+    health: Health
+    status: Status
+    level: Level
+    factions: Set<Faction>
+}
+
+------------------------------------------------------------
+-- Rules
+------------------------------------------------------------
+
+rule CharacterCreation {
+    when: Character.create(name, level)
+    ensures: character.health.value = 1000
+    ensures: character.status = alive
+    ensures: character.level = level
+    ensures: character.factions = empty
+}
+
+rule HealthNonNegative {
+    for c in Characters:
+        c.health.value >= 0
+}
+
+rule StatusAliveImpliesHealthPositive {
+    for c in Characters:
+        c.status = alive implies c.health.value > 0
+}
+
+rule StatusDeadImpliesHealthZero {
+    for c in Characters:
+        c.status = dead implies c.health.value = 0
+}
+
+rule MaxLevel {
+    for c in Characters:
+        c.level.value <= 10
+}
+
+rule MinLevel {
+    for c in Characters:
+        c.level.value >= 1
+}