Part of local coop implementation #1

For a local co-op experience (Cuphead-like), the camera cannot be a child of Player 1. It must dynamically track the center point between all active players and zoom out if they get too far apart (or restrict movement if edge-clamping is preferred)

Acceptance Criteria:

•  Camera creates a bounding box around all active players
•  Camera centers on the average position of players
•  Players are blocked from leaving the screen bounds (or camera zooms out)