Broaden SO_PREFIXES to (so100, so101, so_, bi_so_) so bimanual two-arm datasets
(robot_type 'bi_so_follower', 12-dim) are recognized as SO and get the degrees
conversion, instead of being skipped as non_so. so_ boundary avoids matching
stray names like 'sofa'.
Split classify() into reusable pieces: is_so_robot_type() for the robot_type
name test, and encoding_from_bounds() as the single source of truth for the
degrees_old/degrees_new/normalized/radians decision from per-joint min/max
(layout-agnostic, so v2.1 episodes_stats and v3.0 stats.json both feed it).
CarolinePascal