Phase 1: tighten the splatter shooting loop

Input during the 'over' beat is no longer swallowed: a tap/flick while
G.phase==='over' (splatter only) resets inline and falls through to the
serve logic, so the finger is the only cadence limit. Spent balls
(lastHit 'X' after a stagger bounce) and hopeless balls (out of the
z/x bounds) are retired immediately instead of lingering until they roll
out. New TUNE.splatterOverT (0.1) replaces the hardcoded 0.25 over-timer.

The out-of-bounds z-bounds gate on travel direction so a quick-serve born
behind the baseline (P.z up to 26, heading vz<0 to the far court) isn't
killed on frame one.

Verified via window.T: flick/tap during 'over' serves same frame; spent
ball dies the frame it bounces; serve->serve latency 0 frames with
immediate flicks; tennis 'over' unchanged (2.2s pause, tap ignored);
tennis CPU still returns 11/12 serves; no console errors.

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

config.js

@@ -22,6 +22,7 @@ export const TUNE = {
   zMax: 6,          // shamblers on court at once
   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
   missHud: 1,       // show the last miss reason on screen (full log: T.G.missLog)
 };