Environments

Grid-world environments for cooperative tasks.

GridWorld	Multi-agent grid environment with dynamic reward activation and penalties.
GridWorld_r0	Regime 0: Single-step reward at center regardless of target labels.
GridWorld_r1	Regime 1: Single target 'rl' activated after center.
GridWorld_r2	Regime 2: Single target 'ud' activated after center.
GridWorld_r3	Regime 3: Multiple directional targets after center.