refactor: remove skill system leftovers, migrate click mana to discipline perk

- Simplified getMeditationBonus() to continuous ramp formula
- Added click-mana capped perk to Mana Circulation discipline
- Removed manaWell/manaFlow/manaSpring skill reads and prestige upgrades
- Removed all skill fields from GameState and GameActionType
- Updated all call sites and tests (916 tests passing)

Closes #174

src/components/game/tabs/PrestigeTab.test.ts

@@ -28,9 +28,9 @@ describe('Tab barrel export', () => {
 // ─── Test: Prestige upgrade definitions ────────────────────────────────────────
 
 describe('Prestige upgrade definitions', () => {
-  it('has exactly 13 prestige upgrades', async () => {
+  it('has exactly 11 prestige upgrades', async () => {
     const { PRESTIGE_DEF } = await import('@/lib/game/constants/prestige');
-    expect(Object.keys(PRESTIGE_DEF).length).toBe(13);
+    expect(Object.keys(PRESTIGE_DEF).length).toBe(11);
   });
 
   it('all upgrades have required fields', async () => {
@@ -43,10 +43,10 @@ describe('Prestige upgrade definitions', () => {
     }
   });
 
-  it('all 14 expected upgrade IDs are present', async () => {
+  it('all 11 expected upgrade IDs are present', async () => {
     const { PRESTIGE_DEF } = await import('@/lib/game/constants/prestige');
     const expectedIds = [
-      'manaWell', 'manaFlow', 'insightAmp', 'spireKey',
+      'insightAmp', 'spireKey',
       'temporalEcho', 'steadyHand', 'ancientKnowledge', 'elementalAttune',
       'spellMemory', 'guardianPact', 'quickStart', 'elemStart',
       'unlockedManaTypeCapacity',