Let the player choose a court before the match

Three courts, picked on a second start-screen stage: CENTRE COURT (grass),
TERRE ROUGE (clay) and THE SLAB (hard). A court is a row in config.COURTS and
four PNGs — render() never learns their names.

Each row carries two palettes, because every court still rots: what "drained"
means on orange clay is not what it means on green lawn. Mow stripes became a
flag rather than a colour — recolouring the lawn and leaving the bands on still
read as grass. Bounce is two numbers copied into TUNE on selection, so the three
bounce sites in gameplay.js and the T panel stay untouched: grass skids low and
fast, clay sits up and drags, hard is the old baseline.

Per-court crowd sheets and ad strips. Each court's clap frame is generated from
its OWN seated sheet, not from x_crowd2 — pairing one court's crowd with
another's applause cross-fades between two different crowds.

The picker is a second panel in the existing #intro overlay, rows built from the
table. Last pick is remembered and comes up pre-highlighted; 1..N or Enter on a
keyboard.

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

state.js

@@ -1,6 +1,6 @@
 // All mutable game state in one place, plus the point-reset that re-arms it.
 
-import { HOME, BOY_ENTER, TUNE, COURT } from './config.js';
+import { HOME, BOY_ENTER, TUNE, COURT, COURTS } from './config.js';
 import { gore } from './zombies.js'; // runtime-only cycle (zombies imports state): sendBoy reads gore
                                      // to decide whether a mopping round is worth walking out for
 
@@ -11,6 +11,17 @@ export const ball = { x: 0, y: 1, z: 20, vx: 0, vy: 0, vz: 0, g: 9.2,
 export const score = { pts: [0, 0], games: [0, 0], server: 'P' }; // pts index 0=P 1=O
 export const crowd = { cheer: 0, dots: [] }; // dots are (re)built by render.buildCrowd
 
+// The court you picked on the start screen. Everything visual reads `court` directly; the two
+// bounce numbers are COPIED INTO TUNE instead, so the T panel still edits the live physics and
+// gameplay's three bounce sites stay untouched.
+export let court = COURTS[0];
+export function selectCourt(id) {
+  court = COURTS.find(c => c.id === id) || COURTS[0];
+  TUNE.bounceY = court.bounceY; TUNE.bounceXZ = court.bounceXZ;
+  try { localStorage.setItem('court', court.id); } catch {} // private mode: a forgotten pick is fine
+  return court;
+}
+
 // everything that used to be loose top-level lets
 export const G = {
   mode: 'tennis',     // tennis | transition | splatter