Animate the summer sun: rays breathe + glisten

Details

Split the baked sun into two layers — a static base (corona + bloom +
halo + disc) and a separate rays layer — so the rays can be transformed
per frame cheaply (just drawImage, no gradient rebuilds):
- Rays gently 'breathe' (subtle size oscillation) and shimmer (alpha
  pulse), with a slow rotation.
- A faint offset second blit at a different phase makes them sparkle/
  glisten like real sunlight.
Verified the sun region changes frame-to-frame; perf unchanged (still
two-to-three cheap blits at the 33fps ambient cap).

Files changed (1)