Draw the whole serve right-handed, and let the pull wind it up

The racket kept changing hands because the art disagreed with itself: p_idle,
p_bounce and p_toss held it in his LEFT hand while p_smash and p_swing used his
right, so every new frame copied whichever reference it was handed. The idle, the
bounce pair, the toss and the four wind-up frames are all regenerated with the
side named — drawn from behind, his right hand is the right-hand side of the
image, and only the racket HEAD crosses behind his back.

What separates the four wind-up stages is how far the racket has fallen, and that
needed the racket head pinned to a body landmark per frame — above his head,
beside his ear, between his shoulder blades, at the back of his thighs. Described
as "further into it each time" it drew four near-identical poses twice running.
They are wired late in the pull, Oliver's call: frame 1 owns the first half and
the three coiled frames are packed into the top half.

assets/_derive.py is deleted. Fixing generated art by mangling it afterwards is
always worse than regenerating; three guards in _regen.py turn the bad rolls that
used to install silently into automatic re-rolls — a portrait reference canvas
(the generator answered with a 2x2 grid), a non-magenta background (a green sheet
keyed away four racket heads), and a mirrored frame.

The bounce pair is one drawing from one sheet now, differing only in the free
hand, so BOUNCE_IDLE moved to his left side and was re-measured off the sprite.

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

gameplay.js

@@ -132,7 +132,11 @@ function doHit(ch, quality, aim) {
 // ----------------------------------------------------------------- serve ----
 function tossBall(sv) {
   ball.active = true; ball.bounces = 0; ball.firstLand = null; ball.collected = false;
-  ball.x = sv.x + 0.35 * (sv.side === 'P' ? 1 : -1); ball.z = sv.z; ball.y = TOSS.y0;
+  // The player is right-handed: he tosses with his LEFT hand (viewer's left) and hits with the
+  // racket on the viewer's right, so the ball goes up almost over his head — a big offset either way
+  // lands it on the wrong side of one of those two frames. The opponent is drawn from the front and
+  // keeps the reach he was drawn with.
+  ball.x = sv.x + (sv.side === 'P' ? 0.12 : -0.35); ball.z = sv.z; ball.y = TOSS.y0;
   ball.vx = 0; ball.vz = 0; ball.vy = TOSS.vy; ball.g = TUNE.gravity;
   G.phase = 'toss';
 }
@@ -793,7 +797,7 @@ export function dragServe(aim) {
   if (ball.active && G.phase !== 'toss') // the old ball flies on as a ballistic clone
     extras.push({ x: ball.x, y: ball.y, z: ball.z, vx: ball.vx, vy: ball.vy, vz: ball.vz, pow: ball.pow || 0.5, t: 2.5, g: ball.g });
   ball.active = true; ball.collected = false; ball.bounces = 0; ball.firstLand = null;
-  ball.x = P.x + 0.35; ball.z = P.z; ball.y = 2.2; ball.g = TUNE.gravity;
+  ball.x = P.x + 0.12; ball.z = P.z; ball.y = 2.2; ball.g = TUNE.gravity; // over his head, see tossBall
   hitServe(P, pullQuality(aim.mag), aim); // a full pull is quality 1.0 — PERFECT, hitstop and all
 }