docs: add user story observations and implementation order

doc/user-story-observations.md

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+# User Story Observations
+
+## Domain Model Overview
+
+The domain has **four core entities**:
+
+| Entity | Key Properties |
+|---|---|
+| **Character** | Health (max 1000/1500), Level (1–10), Alive/Dead, Factions (many), damage survived, faction count |
+| **Magical Object** | Health, maxHealth, type (Healing or Weapon), destroyed flag |
+| **Faction** | String/name, members |
+| **Damage/Heal events** | Source, target, amount, level-adjusted |
+
+---
+
+## User Story Groups
+
+### 1. Damage & Health (3 rules)
+- Characters start at 1000 HP, Alive
+- Damage subtracts from HP; death at 0
+- Self-damage forbidden
+- Healing: self only, dead can't heal
+
+### 2. Levels (2 rules)
+- Base level 1; max HP scales at level 6 (→ 1500)
+- Level gap ≥ 5: damage ±50% (target higher = -50%, target lower = +50%)
+
+### 3. Factions (3 rules)
+- Characters can join/leave multiple factions
+- Same faction = Allies: no damage between allies, ally-only healing
+
+### 4. Magical Objects (3 rules)
+- **Healing objects**: give HP to characters, can't deal damage, can't be healed
+- **Weapons**: deal fixed damage, lose 1 HP per use, can't heal
+- Objects are faction-neutral
+
+### 5. Leveling Up (3 rules)
+- **Survived damage**: Level 1 → 1000, then +2000 per level (cumulative)
+- **Faction diversity**: Level 1 → 3 factions, then +3 per level (cumulative)
+- Max level 10, no level loss
+
+---
+
+## Observations & Ambiguities
+
+1. **Max HP scaling**: Only mentions the jump at level 6. What about levels 7–10? Is max HP flat at 1500, or does it increase further?
+
+2. **Level gap rule**: "5 or more levels" — is it strictly `≥ 5` or `> 5`? The wording says "5 or more" so `≥ 5`.
+
+3. **Survived damage counter**: Is it per-character global (across all battles), or per-battle? The story says "counted over several battles" → global.
+
+4. **Faction diversity counter**: "ever been part of" — cumulative across the character's lifetime, not just current factions.
+
+5. **Level-up timing**: "happens directly afterwards (if the player is still alive)" — level-ups are synchronous, not deferred.
+
+6. **Magical Object durability**: Weapons lose 1 HP per use — does that mean they can be "used" until destroyed (HP = 0)? Healing objects presumably can also be depleted.
+
+7. **Healing cap**: Characters heal up to their max HP (which depends on level), and objects heal up to their own max.
+
+8. **No explicit interface**: The stories describe behavior but don't specify method signatures — we'll need to design the API.
+
+---
+
+## Suggested Implementation Order
+
+1. **Character** (HP, level, alive state, factions)
+2. **Damage/Heal mechanics** with faction ally checks
+3. **Level-based damage modifiers**
+4. **Magical Objects** (Weapons + Healers)
+5. **Leveling up** (survived damage + faction diversity)