feat: integrate skill tree UI and combat bonuses

Grant skill points on floor clear, add allocation UI with [ ] keys
during exploration, apply SkillPower bonus to Mage Fireball and Healer
Heal, initialize skills for new players, and deep copy skills in
GetState.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

game/session.go

@@ -199,6 +199,9 @@ func (s *GameSession) signalCombat() {
 func (s *GameSession) AddPlayer(p *entity.Player) {
 	s.mu.Lock()
 	defer s.mu.Unlock()
+	if p.Skills == nil {
+		p.Skills = &entity.PlayerSkills{BranchIndex: -1}
+	}
 	s.state.Players = append(s.state.Players, p)
 }
 
@@ -231,6 +234,10 @@ func (s *GameSession) GetState() GameState {
 		copy(cp.Relics, p.Relics)
 		cp.Effects = make([]entity.ActiveEffect, len(p.Effects))
 		copy(cp.Effects, p.Effects)
+		if p.Skills != nil {
+			skillsCopy := *p.Skills
+			cp.Skills = &skillsCopy
+		}
 		players[i] = &cp
 	}
 
@@ -337,6 +344,21 @@ func (s *GameSession) TouchActivity(fingerprint string) {
 	s.lastActivity[fingerprint] = time.Now()
 }
 
+// AllocateSkillPoint spends one skill point into the given branch for the player.
+func (s *GameSession) AllocateSkillPoint(fingerprint string, branchIdx int) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	for _, p := range s.state.Players {
+		if p.Fingerprint == fingerprint {
+			if p.Skills == nil || p.Skills.Points <= p.Skills.Allocated {
+				return fmt.Errorf("no skill points available")
+			}
+			return p.Skills.Allocate(branchIdx, p.Class)
+		}
+	}
+	return fmt.Errorf("player not found")
+}
+
 // BuyItem handles shop purchases
 func (s *GameSession) BuyItem(playerID string, itemIdx int) bool {
 	s.mu.Lock()

game/turn.go

@@ -147,10 +147,15 @@ func (s *GameSession) resolvePlayerActions() {
 				}
 				s.addLog(fmt.Sprintf("%s used Taunt! Enemies focus on %s for 2 turns", p.Name, p.Name))
 			case entity.ClassMage:
+				skillPower := 0
+				if p.Skills != nil {
+					skillPower = p.Skills.GetSkillPower(p.Class)
+				}
+				multiplier := 0.8 + float64(skillPower)/100.0
 				intents = append(intents, combat.AttackIntent{
 					PlayerATK:  p.EffectiveATK(),
 					TargetIdx:  -1,
-					Multiplier: 0.8,
+					Multiplier: multiplier,
 					IsAoE:      true,
 				})
 				intentOwners = append(intentOwners, p.Name)
@@ -170,8 +175,12 @@ func (s *GameSession) resolvePlayerActions() {
 						}
 					}
 				}
+				healAmount := 30
+				if p.Skills != nil {
+					healAmount += p.Skills.GetSkillPower(p.Class) / 2
+				}
 				before := target.HP
-				target.Heal(30)
+				target.Heal(healAmount)
 				s.addLog(fmt.Sprintf("%s healed %s for %d HP", p.Name, target.Name, target.HP-before))
 			case entity.ClassRogue:
 				currentRoom := s.state.Floor.Rooms[s.state.Floor.CurrentRoom]
@@ -356,6 +365,13 @@ func (s *GameSession) advanceFloor() {
 		s.addLog("You conquered the Catacombs!")
 		return
 	}
+	// Grant 1 skill point per floor clear
+	for _, p := range s.state.Players {
+		if p.Skills == nil {
+			p.Skills = &entity.PlayerSkills{BranchIndex: -1}
+		}
+		p.Skills.Points++
+	}
 	s.state.FloorNum++
 	s.state.Floor = dungeon.GenerateFloor(s.state.FloorNum, rand.New(rand.NewSource(time.Now().UnixNano())))
 	s.state.Phase = PhaseExploring