Stadium pass: real crowd, sponsor boards, umpire visible in portrait

- Umpire chair moved courtside (UMP_X 5.6, was 7.1 — which projected to
  x=272 on a 270px-wide portrait canvas: literally one pixel off-screen).
  Tap-cheat coords follow the constant.
- Generated pixel-art night crowd (x_crowd.png) replaces the tier stripes +
  random dots; drawn in 16 columns that bounce independently while the crowd
  cheers. Old procedural crowd kept as the loading fallback.
- Generated courtside sponsor boards (x_ads.png): ACEADE, TOPSPIN & CO,
  VOLLEX, NETTO GRIP, SLAMWICH — tiled at native aspect so lettering is
  never half-cut at any viewport width. Replaces the 'SPLATTER OPEN' text.
- One rot tint over crowd + boards driven by the shared paletteT() (new
  helper), so the stadium dims into splatter and brightens back for duels.

Verified: fresh origin; tennis + splatter screenshots (boards tile cleanly,
crowd reads, tint dims, umpire on-screen beside the court); umpire triple-tap
works at the new chair position; tennis serve benchmark 33/36 across two runs
(first 12 was flub noise); no console errors.

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

main.js

@@ -3,7 +3,7 @@
 // Module map: config (tuning/constants) · state (mutable game state) · gameplay (logic/update)
 //             render (camera/drawing) · input (keys/touch) · audio (sfx/umpire) · panel (T tuning UI)
 
-import { TUNE, COURT, UMP_H } from './config.js';
+import { TUNE, COURT, UMP_H, UMP_X } from './config.js';
 import { P, O, ball, score, G, setupPoint } from './state.js';
 import { update, keyPressed, solveShot, inServeBox, inCourt, forceZombies, splatPoint } from './gameplay.js';
 import { fitViewport, render, proj, RES } from './render.js';
@@ -43,7 +43,7 @@ cv.addEventListener('pointerdown', e => {
   const x = (e.clientX - r.left) / r.width * (cv.width / RES);  // logical coords
   const y = (e.clientY - r.top) / r.height * (cv.height / RES);
   if (x >= 6 && x <= 138 && y >= 6 && y <= 36) { G.logShow = !G.logShow; return; } // scoreboard tap = miss-log overlay
-  const u = proj(7.1, 0, COURT.netZ);
+  const u = proj(UMP_X, 0, COURT.netZ);
   if (Math.abs(x - u.x) > 16 || y > u.y + 6 || y < u.y - UMP_H * u.s - 8) return;
   const now = performance.now();
   umpTaps = umpTaps.filter(t => now - t < 1600);