Fix the freeze; duel intro card + tennis lights; hold-to-aim; instant gun steering

THE FREEZE (root cause found): the game-winning kill fires INSIDE the zombie
update loop — killZombie -> splatPoint -> gameOver -> sweepCourt guts the
zombies array mid-iteration, the loop reads zombies[i] === undefined, throws,
and the un-rescheduled RAF chain dies: a permanent hard freeze. Crowded courts
(later games, brutes) make the mid-loop game-winner likelier — hence 'freezes
around game 3 when the fat zombies arrive'. Fixed at the root (null guards in
every loop whose body can cascade into a sweep: zombie walk loop, meleeSwipe,
explode, pellet + extras inner loops) AND made frame() reschedule RAF FIRST so
no single bad frame can ever kill the loop again.

Aim awareness: the reticle now appears the moment the thumb lands (mag 0 =
auto-target the most advanced zombie, red lock immediately). A pure HOLD
(>250ms, no drag) releases into the auto-target serve; dragging aims as
before; the serve prompt switches to 'RELEASE TO SERVE / RELEASE FIRES THE
BOMB - DRAG BACK TO CANCEL' while aiming.

Duel presentation: the interlude now opens with a 2.4s intro beat — serving
blocked, centered card (SUDDEN DEATH / ONE POINT - THE LINES ARE LIVE / WIN
IT FOR THE NEXT TIN), and the palette lerps back to the TENNIS colors for
the duration of the duel (duelLerp, 0.8s each way) — order visibly restored,
then the rot returns.

Machine-gun steering: absolute now — the finger x IS the player x, zero lag
(was sign-quantized velocity). Clamped to what the camera can see
((W/2-14)/proj-scale — portrait's world bounds are wider than its viewport),
keyboard steering clamped the same during auto-fire.

Verified: the exact pre-fix crash scenario (game-winning kill mid-loop,
9 zombies + brute) survives and sweeps clean; intro blocks taps then the
duel plays; hold-release fired at the auto-lock and won a tin end-to-end;
screenshot shows tennis-green court + centered card + GAME 2; MG jumps
P.x to the finger in one frame, clamped; tennis 12/12; no console errors.

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

main.js

@@ -14,9 +14,9 @@ import './input.js';
 
 let last = performance.now();
 function frame(now) {
+  requestAnimationFrame(frame); // schedule FIRST: one bad frame must never kill the loop (a thrown error froze the game for good)
   const dt = Math.min(0.033, (now - last) / 1000); last = now;
   update(dt); render();
-  requestAnimationFrame(frame);
 }
 
 fitViewport();