fix: defensive hardening — NaN guards, cast loop safety, discipline reset on new loop, spire mode maxFloorReached fix

src/lib/game/stores/combatStore.ts

@@ -200,7 +200,7 @@ export const useCombatStore = create<CombatStore>()(
 
       enterSpireMode: () => {
         const freshRoom = generateSpireFloorState(1, 0, 1);
-        set({
+        set((s) => ({
           spireMode: true,
           currentAction: 'climb',
           currentFloor: 1,
@@ -211,7 +211,8 @@ export const useCombatStore = create<CombatStore>()(
           climbDirection: null,
           isDescending: false,
           clearedFloors: {},
-        });
+          maxFloorReached: Math.max(s.maxFloorReached, s.currentFloor),
+        }));
       },
 
       learnSpell: (spellId: string) => {