Phase 11: enemy roster wired — runner, brute, shield zombie

- Spawn mix (pickVariant): roster grows one type per set — runner from set 1
  game 3+ (12% slot, at most one alive, shriek on spawn = the fairness contract),
  brute from set 2 (15%), shield from set 3 (15%); classics fill the rest
- Runner ('f'): 3.2x shamble speed, faster leg cycle; new shriek() synth in audio
- Brute ('g'): hp 2 vs splat-quality balls AND pellets, 0.55x speed, 0.75m target,
  pushback-immune, 0.9m eaten radius, dies to double gore + size-2 pile, towers
  at 1.5x height
- Shield ('s'): blocks front balls with the chair (clank, ball spent), the block
  drops the chair for shieldDown 1.5s — any splat-quality ball kills in the
  window (z_s3 staggered pose renders); chair recovers after; always dies to
  bombs, melee, pellets
- TUNE: runnerSpeed 3.2, bruteHp 2, shieldDown 1.5

Verified in browser: per-variant stats; brute soft-ball immunity, 2-hit kill,
2-pellet kill, size-2 pile; shield block->window kill->chair recovery->blocks
again; melee kills f/s but not the racket boss; tier-2 spawn mix over 1500
spawns = 14/15/8/63%; all five sprites render with correct scale+occlusion;
tennis regression 11/12; no console errors.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

config.js

@@ -35,6 +35,9 @@ export const TUNE = {
   hordeLen: 12,     // s a horde wave lasts
   hordeRate: 2.5,   // zombies spawned per second during a horde
   mgRate: 6,        // machine-gun pellets fired per second during a horde
+  runnerSpeed: 3.2, // runner ('f') speed multiplier over the shamble
+  bruteHp: 2,       // splat-quality hits (or pellets) a brute ('g') soaks before it dies
+  shieldDown: 1.5,  // s a shield zombie's ('s') chair stays dropped after a block — the kill window
   meleeRange: 1.7,  // m — a racket swish cleaves shamblers this close to you
   racketHp: 3,      // splat-quality hits a racket zombie (mini-boss) takes before it dies
   racketSpeed: 2.8, // m/s the racket zombie shambles to chase a ball