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>

dom.js

@@ -0,0 +1,3 @@
+// Canvas handles — imported by everyone, imports nothing (keeps module cycles harmless).
+export const cv = document.getElementById('c');
+export const ctx = cv.getContext('2d');