Split the monolith into ES modules; hoist scattered magic numbers

game.js (830 lines) -> 9 modules, native ES modules so still zero build step:
  dom      canvas handles (imports nothing; keeps cycles harmless)
  config   TUNE (live-tunable) + structural constants
  state    all mutable game state (G) + setupPoint/sendBoy
  audio    sfx synthesis, recorded umpire voice, reverb, speech fallback
  input    keyboard + touch, exports axes and takeFlickAim()
  gameplay ballistics, swings, serve, rules, AI, update loop
  render   camera, viewport, sprites, crowd, all drawing
  panel    T tuning UI
  main     boot, loop, intro, window.T test hooks

Deduped into named constants: bounce tempo (was in 3 places), contact
height band, intercept zone depth, home positions, player bounds, toss
params, shot depths, pose hold time, sprite scale, actor heights. Also
extracted drawShadow/drawBall/expirePose from repeated code.

One intentional import cycle (input <-> gameplay), safe: both sides only
call functions at runtime, never during module evaluation.

Regression-verified in browser sims: point cycle, CPU returns 11/12,
assist contract 8/8, corner-winner gradient intact (0/12 perfect corners
returned, 10/12 center balls returned).

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

panel.js

@@ -0,0 +1,18 @@
+// Live tuning panel (T key): number inputs for every TUNE value.
+
+import { TUNE } from './config.js';
+
+let panel = null;
+export function togglePanel() {
+  if (panel) { panel.remove(); panel = null; return; }
+  panel = document.createElement('div');
+  panel.style.cssText = 'position:fixed;top:8px;right:8px;background:#141a26;color:#cdd6e4;font:11px monospace;padding:8px;border:1px solid #3a4a66;max-height:90vh;overflow:auto';
+  for (const k of Object.keys(TUNE)) {
+    const row = document.createElement('div');
+    const v = TUNE[k];
+    row.innerHTML = `<label>${k} <input type="number" step="${v < 2 ? 0.02 : 1}" value="${v}" style="width:60px;background:#0c1018;color:#fff;border:1px solid #333"></label>`;
+    row.querySelector('input').oninput = e => TUNE[k] = parseFloat(e.target.value) || 0;
+    panel.appendChild(row);
+  }
+  document.body.appendChild(panel);
+}