fix: Golemancy enchantment capacity, design persistence, and UI selectors

- Fix enchantment capacity formula: multiply magicAffinity by 100 (spec treats it as percentage)
- Fix enterSpireMode preserving golemDesigns (only reset loadout/activeGolems per spec §9)
- Add mana type selector UI for Intermediate/Advanced/Guardian cores
- Add spell selector UI for circuits with spell slots

Fixes #310, #311, #312

src/lib/game/stores/combat-descent-actions.ts

@@ -253,7 +253,7 @@ export function createEnterSpireMode(get: GetFn, set: SetFn) {
       roomResetState: {},
       descentPeak: null,
       isDescentComplete: false,
-      golemancy: { activeGolems: [], lastSummonFloor: 0, golemDesigns: {}, golemLoadout: [] },
+      golemancy: { activeGolems: [], lastSummonFloor: 0, golemDesigns: s.golemancy?.golemDesigns ?? {}, golemLoadout: [] },
     });
 
     get().addActivityLog('floor_transition',