fix(ec/sw): correct SWFlags handling in from_random_bytes #1037
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The SW compressed encoding defines YIsPositive when y <= -y (i.e., the smaller y in integer order). During deserialization via Affine::from_random_bytes, the boolean from flags was passed directly into get_point_from_x_unchecked as the “greatest” selector, which chooses the larger y. This inverted the intended sign convention only on this code path.
Fix: invert the boolean when reconstructing from flags (pass !y_is_positive to get_point_from_x_unchecked), aligning from_random_bytes with the main serialize/deserialize path.
Added tests:
behavior now consistent across all SW serialization/deserialization paths.