Stabilize player/obstacle collision resolution in Commit Dash

[Copilot]

Collision handling was intermittently unstable: collisions were resolved against stale obstacle positions, and overlap tie cases could flip resolution axes frame-to-frame. This update makes collision resolution deterministic and aligned with current world positions.

• Update order: resolve against current obstacle positions

  • Move world scrolling ahead of grounded/collision checks in update() so collision math runs on the latest tile coordinates.

• Deterministic overlap resolution

  • Replace strict min-overlap equality checks with explicit horizontal vs vertical overlap comparison.
  • Introduce a small axis bias (COLLISION_AXIS_BIAS) to prefer vertical resolution in near-tie cases, reducing edge jitter/clipping.

• Configuration clarity

  • Add GAME_CONFIG.COLLISION_AXIS_BIAS and use it in checkGrounded() instead of an inline magic number.

const minHorizontalOverlap = Math.min(overlapLeft, overlapRight);
const minVerticalOverlap = Math.min(overlapTop, overlapBottom);
const shouldResolveVertically =
  minVerticalOverlap <= (minHorizontalOverlap + GAME_CONFIG.COLLISION_AXIS_BIAS);

if (shouldResolveVertically) {
  // top/bottom resolution
} else {
  // side resolution
}