Pets: per-round attack + wire deflect/whiff into the turn engine

The live turn engine only struck once per fight and never rolled pet
deflect or whiff, so pet armor (deflect-only) bought nothing in real
runs. Roll pet attack each player turn and roll deflect/whiff per enemy
turn, mirroring the auto-resolve engine; retire the one-shot pet-proc
machinery (rollCombatSessionPetProc / PetProcReady).

(cherry picked from commit a0e41c97801e500efad13c7e9a06be4c345e464e)

internal/plugin/combat_engine.go

@@ -319,10 +319,6 @@ type combatState struct {
 	// the enemy would otherwise attack).
 	enemySkipFirst bool
 
-	// Phase 13 turn-based — pet attack decided once at fight start; the pet
-	// strikes once on the player's first acting turn, which clears this.
-	petProcReady bool
-
 	// Phase 10 SUB2a-ii first-attack one-shots.
 	firstAttackBonusUsed  bool
 	assassinateRerollUsed bool