Zombie mode: kills-per-point knob so a game isn't 4 pot-shots

1 kill = 1 point made a tennis game trivially short (4 kills). Gate
player scoring behind TUNE.killsPerPoint (default 3) — K kills bank one
point, the rest just splatter. Opponent breaches stay 1-for-1, so the
asymmetry is where the pressure comes from. Live-tunable in the T panel;
set to 1 to restore the old behavior.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

config.js

@@ -27,6 +27,7 @@ export const TUNE = {
   gameBeatT: 1.6,   // s the game-end beat lasts on even (non-changeover) games
   eatenR: 0.9,      // m a shambler must close to eat you — matches the visual sprite overlap
   zSnap: 1.4,       // m free-aim magnetism: a zombie this close to your flick's landing point is the target
+  killsPerPoint: 3, // splatter: zombie kills to score ONE tennis point (1 = every kill scores, old behavior)
   zSplatQ: 0.5,     // min shot quality to splatter; below = stagger pushback
   zPushback: 1.4,   // m a staggered zombie is knocked back
   splatterOverT: 0.1, // s the spent-ball 'over' beat lasts before the next serve is armed