Remove familiar system completely

- Delete familiar-slice.ts, familiars.ts, and FamiliarTab.tsx
- Remove familiar types from types.ts (FamiliarRole, FamiliarAbilityType, FamiliarAbility, FamiliarDef, FamiliarInstance)
- Fix SpireTab spell effects to show valid types (burn, stun, pierce, multicast, buff) instead of invalid lifesteal/freeze
- Remove Executioner test from store.test.ts (execute effect was previously removed)
- Remove familiar fields from skills.test.ts mock state

Familiars detract from the Invoker pact system. The familiar system was
incomplete (missing state fields) and referenced removed ability types.

src/lib/game/store.test.ts

@@ -1972,16 +1972,6 @@ describe('Special Effect Application', () => {
   });
   
   describe('Combat Special Effects', () => {
-    it('should recognize Executioner special effect', () => {
-      const state = createMockState({ 
-        skills: { combatTrain: 10 },
-        skillUpgrades: { combatTrain: ['ct_t1_l10_execute'] }
-      });
-      
-      const effects = computeEffects(state.skillUpgrades, state.skillTiers || {});
-      expect(hasSpecial(effects, SPECIAL_EFFECTS.EXECUTIONER)).toBe(true);
-    });
-    
     it('should recognize Berserker special effect', () => {
       const state = createMockState({ 
         skills: { combatTrain: 10 },