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/lib/game/constants/core.ts

@@ -16,12 +16,11 @@ export const RARITY_COLORS: Record<string, string> = {
   mythic: '#EF4444',
 };
 
-// ─── Study Speed Formula ─────────────────────────────────────────────────────
-export function getStudySpeedMultiplier(skills: Record<string, number>): number {
-  return 1 + (skills.quickLearner || 0) * 0.1;
+// ─── Study Multipliers (skill system removed, always base value) ────────────
+export function getStudySpeedMultiplier(): number {
+  return 1;
 }
 
-// ─── Study Cost Formula ───────────────────────────────────────────────────────
-export function getStudyCostMultiplier(skills: Record<string, number>): number {
-  return 1 - (skills.focusedMind || 0) * 0.05;
+export function getStudyCostMultiplier(): number {
+  return 1;
 }

src/lib/game/constants/prestige.ts

@@ -2,8 +2,6 @@
 import type { PrestigeDef } from '../types';
 
 export const PRESTIGE_DEF: Record<string, PrestigeDef> = {
-  manaWell:     { name: "Mana Well",     desc: "+500 starting max mana",     max: 5,  cost: 500 },
-  manaFlow:     { name: "Mana Flow",     desc: "+0.5 regen/sec permanently", max: 10, cost: 750 },
   insightAmp:   { name: "Insight Amp",   desc: "+25% insight gain",          max: 4,  cost: 1500 },
   spireKey:     { name: "Spire Key",     desc: "Start at floor +2",          max: 5,  cost: 4000 },
   temporalEcho: { name: "Temporal Echo", desc: "+10% mana generation",       max: 5,  cost: 3000 },