Phase 4: bomb balls

Ball boys deliver a bomb ball every TUNE.bombEvery (8) splatter kills, up
to TUNE.bombMax (3) in stock (G.bombs / G.killMeter in state). The next
serve auto-consumes one (hitServe, splatter-only) — no extra input, keeping
one-handed play. A bomb detonates on first zombie contact (regardless of
pace) or, if it misses everyone, on its first bounce: explode() splatters
everything within TUNE.bombRadius (2.5m), each kill feeding ball.kills so
the Phase-2 fanfare escalates naturally, and leaves a crater — big stain,
size-3 pile, 40 particles, 0.1s hitstop, boom(). New synth boom() in
audio.js. Bomb ball renders black with a flickering orange fuse; the HUD
shows stocked bombs as black/orange pips by the YOU line. Both explode
sites set phase='over' so the serve loop doesn't stall on the killed ball.

Alternative delivery ideas Oliver floated but not built: umpire throws it,
or court pickup.

Verified via window.T: 8th kill earns a bomb (meter resets); a serve
consumes one and renders #111 black + orange fuse; a pow-0 bomb amid 4
clustered zombies kills all 4 with 'MASSACRE ×4', boom, hitstop 0.1,
crater stain (r1.4) + size-4 pile; a bomb that misses still craters on
first bounce; bombs never leak into tennis (mode guard); 3 HUD pips; no
console errors.

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

state.js

@@ -5,7 +5,7 @@ import { HOME } from './config.js';
 export const P = { x: 1.3, z: 22.8, side: 'P', pose: 'idle', poseT: 0, swingT: -1, facing: 1, runT: 0 };
 export const O = { x: -1.3, z: 1.0, side: 'O', pose: 'idle', poseT: 0, swingT: -1, facing: 1, runT: 0 };
 export const ball = { x: 0, y: 1, z: 20, vx: 0, vy: 0, vz: 0, g: 9.2,
-  active: false, lastHit: 'P', bounces: 0, firstLand: null, collected: false, kills: 0 };
+  active: false, lastHit: 'P', bounces: 0, firstLand: null, collected: false, kills: 0, bomb: false };
 export const score = { pts: [0, 0], games: [0, 0], server: 'P' }; // pts index 0=P 1=O
 export const crowd = { cheer: 0, dots: [] }; // dots are (re)built by render.buildCrowd
 
@@ -29,6 +29,8 @@ export const G = {
   aiReactT: 9,        // time since the player's last hit; CPU reads the shot after TUNE.aiReaction
   wasServe: false,    // the ball in flight is a serve (first bounce must hit the box)
   splatT: 0,          // time survived in splatter mode — drives the difficulty ramp
+  bombs: 0,           // bomb-ball stock (max TUNE.bombMax); the next serve auto-consumes one
+  killMeter: 0,       // splatter kills toward the next bomb reward (every TUNE.bombEvery)
   eatenT: 0,          // time since you were eaten — gates the restart tap
   missLog: [],        // swing diagnostics ring buffer (tennis mode) — inspect via T.G.missLog
   swingSnaps: null,   // ball-approach samples during the live swing, feeds the miss log