refactor: restructure proteus into game/web subpackages

feat(cp8): time_to_capture/distance_auc/min_distance/near_capture_count metrics

feat(cp6): trajectory + category-reward metrics (away_move_fraction, trajectory_agreement, ...)

test(cp3): cover perfect/all-diagnostic/cap/empty metrics + single-source divergence

feat(cp3): session metrics (motive-reading, reactivity, survival, divergence)