Runner is glass; battery pass (30fps cap, cached piles, GC fixes)

Runner counter (no new weapon needed — one you don't hold when it shrieks
can't save you): the sprinter is now a GLASS CANNON — any ball contact at
any quality bursts it (main ball and triple-serve side balls; melee and
pellets already killed it). The hold-to-aim auto-lock targets the most
advanced zombie = the charging runner, so touch-and-release is the panic
button. Plus runnerVMax 4.2: the late-game speed ramp is capped so runners
stay humanly reactable.

Battery (iPhone drain):
- TUNE.fps = 30 (T-panel tunable, 0/60 = uncapped): frame-skip cap in the
  RAF loop — halves paint work on a 810x1440 canvas, the dominant cost.
  dt clamp raised 0.033 -> 0.04 so 30fps doesn't run 1% slow-motion.
- Gore piles pre-rendered to per-pile cached canvases (rebuilt on growth /
  orientation change): 1 drawImage per pile per frame instead of ~26
  ellipse paths — late-game courts had ~800 path fills per frame.
- matchMedia('(pointer: coarse)') hoisted out of the render loop (was
  allocating a MediaQueryList every pretoss frame).

Verified: weak (pow .05) ball kills a runner; max-ramp runner v = 4.2
exactly; piles render from cache (screenshot, pl.cv set); frame-cap
arithmetic yields clean every-other-tick at 60Hz RAF (RAF itself is paused
in this pane — logic deterministic); tennis serve benchmark 30/36 across
runs (flub-band; diff is provably tennis-neutral); no console errors.

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

config.js

@@ -39,7 +39,9 @@ export const TUNE = {
   hordeRate: 2.5,   // zombies spawned per second during a horde
   mgRate: 6,        // machine-gun pellets fired per second during a horde
   mgPickupLen: 8,   // s the machine-gun tin (4th delivery) auto-fires outside hordes
+  fps: 30,          // frame cap — pixel art reads fine at 30 and it halves battery/heat; set 60 to compare
   runnerSpeed: 3.2, // runner ('f') speed multiplier over the shamble
+  runnerVMax: 4.2,  // hard runner speed cap — the late-game ramp must stay humanly reactable
   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