Master talents: experience, points and four branches (Builder, Warlord, Warlock, Merchant) with a toolbar window

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/spells.rs

@@ -92,7 +92,7 @@ impl Game {
     }
 
     pub fn cast(&mut self, spell: Spell, wx: f32, wy: f32) {
-        let cost = spell.cost();
+        let cost = spell.cost() * self.talents.spell_cost();
         if self.mana < cost {
             self.msg("msg.no_mana_cost", vec![(cost as i32).to_string()]);
             self.sfx_ui(Sfx::Error);