Adv 2.0 L4d reader flip: pet helpers off AdvCharacter to PetState

All ten helpers in adventure_pets.go now take PetState (or *PetState
for petGrantXP) instead of *AdventureCharacter. mistyHousingHint takes
raw NPC counters since Misty fields stay on AdvCharacter for a later
phase. mistyReactivatePet returns bool; caller flips both stores.

DeathTransitionParams gained Pet PetState so combat_bridge no longer
touches the DB; arena caller loads PetState. PetState.HasPet() mirrors
AdvCharacter's. petMidnightCheck loads PetState per char.

L4 grep-empty exit criterion now holds for adventure_pets.go.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

internal/plugin/adventure_arena.go

@@ -452,8 +452,10 @@ func (p *AdventurePlugin) resolveArenaDeath(ctx MessageContext, run *ArenaRun, c
 
 	phaseMessages := bossFlowPhaseMessages(bossNarr)
 
+	arenaPet, _ := loadPetState(char.UserID)
 	dt := transitionDeath(DeathTransitionParams{
 		Char:          char,
+		Pet:           arenaPet,
 		Source:        "arena",
 		DeathLocation: "the Arena",
 	})