Put a steward on the court

A new ordinary body between the shambler and the brute: a stadium security
steward in a hi-vis vest, 2.15 m, three hp, a touch slower. Deliberately the
mildest thing in the advanced pool — no wound skins, no special rule to learn —
so he can unlock early (game 4) and thicken the ordinary crowd, which a mix of
two shamblers never did. A fifth of horde spawns come out as stewards too, so a
grown wave is not one body dying at one range.

Sheet generated against the existing shambler walk (assets/_sheet_dwalk.png),
sliced to a 4-frame cycle, so he shambles as smoothly as the crowd he walks in.

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

render.js

@@ -155,7 +155,7 @@ export function proj(x, y, z) {
 
 // ---------------------------------------------------------------- sprites ----
 // assets/<name>.png; game falls back to code-drawn figures until sprites load.
-const SPRV = 50; // asset cache-buster — bump with main.js?v=N (see the img.src note below)
+const SPRV = 51; // asset cache-buster — bump with main.js?v=N (see the img.src note below)
 const SPR = {};
 for (const n of ['p_idle1','p_idle2','p_bounce','p_bounce2','p_toss','p_smash','p_run1','p_run2','p_swing1','p_swing2',
                  'o_idle1','o_idle2','o_bounce','o_bounce2','o_toss','o_smash','o_run1','o_run2','o_swing1','o_swing2',
@@ -169,6 +169,7 @@ for (const n of ['p_idle1','p_idle2','p_bounce','p_bounce2','p_toss','p_smash','
                  'z_judge1','z_judge2','z_judgew','z_judget','z_judgewt',   // boss design 2 (chapter 2, 5, ...)
                  'z_chair1','z_chair2','z_chairw','z_chairt','z_chairwt',   // boss design 3 (chapter 3, 6, ...)
                  'z_a1','z_a2','z_a3','z_a4','z_b1','z_b2','z_b3','z_b4','z_c1','z_c2',
+                 'z_d1','z_d2','z_d3','z_d4', // the steward: bigger body, hi-vis vest, 4-frame walk
                  'z_f1','z_f2','z_f3','z_f4','z_g1','z_g2','z_gw','z_s1','z_s2','z_s3',
                  'z_cw1','z_cw2','z_aw','z_bw', // wounded skins for multi-hit enemies (racket boss, brute, and now the classic shamblers)
                  'w_ball','w_bomb','w_triple','w_fire','w_gun', // weapon-rack icons
@@ -257,7 +258,7 @@ function drawBoy(b) {
   ctx.drawImage(img, -w / 2, -h, w, h);
   ctx.restore();
 }
-const ZFRAMES = { a: 4, b: 4, f: 4 }; // 4-frame walk cycles where sheets exist; the rest stay 2
+const ZFRAMES = { a: 4, b: 4, f: 4, d: 4 }; // 4-frame walk cycles where sheets exist; the rest stay 2
 // The rogue ball machine, on its own generated sheet: a dented hopper cart on wheels with a barrel
 // aimed down-court, and a second frame with the muzzle flashing. Oliver called the first, procedural
 // version "naively painted" — it was four rects, which is fine for fire but not for furniture the
@@ -288,7 +289,7 @@ function drawZombie(zb) {
   // same CYCLE frequency as before — more frames subdivide the stride, they don't speed it up
   let frame = rk && zb.pose === 'swing' ? 2 : Math.floor(zb.walkT * (zb.variant === 'f' ? 6 : 2.6) * N / 2) % N + 1;
   if (zb.variant === 's' && zb.shieldT > 0) frame = 3; // chair dropped — hit it NOW
-  let h = zb.variant === 'g' ? 2.7 : rk ? 1.85 : 1.8; // the brute towers half again over the crowd
+  let h = zb.variant === 'g' ? 2.7 : zb.variant === 'd' ? 2.15 : rk ? 1.85 : 1.8; // the brute towers half again over the crowd; the steward stands between him and it
   if (zb.variant === 'B') h = 1.8 * (zb.scale || 1.5);  // ...and a chapter boss towers over the brute
   // wounded skins: multi-hit enemies show their damage as hp drops (arm off → head gone, still
   // shambling). The blood is NOT painted in — open wounds gush live particles (see bleed() in