Start Space Invaders immediately by removing pre-game animation pipeline

[Copilot]

Space Invaders had a pre-start sequence (emoji burst, timed fade, and trigger-side delay) that blocked immediate play after activation. This change removes that pipeline so gameplay initializes as soon as the launch condition is met.

• Game startup path (space-invaders.js)

  • Removed the intro explosion system and its assets/constants.
  • Replaced delayed/fade-based boot with direct _setupGame(this) in scene create.
  • Enabled immediate interaction by setting the game canvas to pointerEvents: "auto" at creation.

• Trigger behavior (eggs.js)

  • Removed heart growth/transition animation on click progression.
  • Removed post-trigger timeout/opacity transition.
  • On the 5th click, launch now happens synchronously.

// Before: delayed intro pipeline
function _onCreate() {
  const particles = _spawnExplosion(this);
  this.time.delayedCall(5000, () => { /* fade + cleanup */ _setupGame(this); });
}

// After: immediate game init
function _onCreate() {
  _setupGame(this);
}