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/data/golems/golemancy-data.test.ts

@@ -136,7 +136,7 @@ describe('Computed stats', () => {
     expect(stats.magicAffinity).toBe(0.3);
     expect(stats.aoeTargets).toBe(1);
     expect(stats.spellSlots).toBe(0);
-    expect(stats.enchantmentCapacity).toBeCloseTo(0.3);
+    expect(stats.enchantmentCapacity).toBeCloseTo(30); // Earth Frame 30% × Basic Core 1.0
     expect(stats.specialEffect).toBe('none');
     expect(stats.availableManaTypes).toEqual(['earth']);
   });
@@ -153,7 +153,7 @@ describe('Computed stats', () => {
     expect(stats.armorPierce).toBe(0.5);
     expect(stats.magicAffinity).toBe(0.5);
     expect(stats.spellSlots).toBe(2);
-    expect(stats.enchantmentCapacity).toBeCloseTo(1.0);
+    expect(stats.enchantmentCapacity).toBeCloseTo(100); // Steel Frame 50% × Advanced Core 2.0
   });
 
   it('guardian crystalSteelHybrid golem with guardian circuit', () => {
@@ -168,7 +168,7 @@ describe('Computed stats', () => {
     expect(stats.armorPierce).toBe(0.7);
     expect(stats.magicAffinity).toBe(1.0);
     expect(stats.spellSlots).toBe(4);
-    expect(stats.enchantmentCapacity).toBeCloseTo(3.0);
+    expect(stats.enchantmentCapacity).toBeCloseTo(300); // Crystal-Steel Hybrid 100% × Guardian Core 3.0
     expect(stats.specialEffect).toBe('guardianConstruct');
   });