Keep the scaled action space valid for a negative scale

[DenisDrobyshev]

Description

scale_actions_v0 builds the scaled action space by multiplying both bounds in
place:

return Box(low=act_space.low * scale, high=act_space.high * scale)

A negative scale maps [low, high] onto [high * scale, low * scale], so the
two bounds swap places and the low ends up above the high. Gymnasium then
refuses the space from inside its own constructor:

env = supersuit.scale_actions_v0(gym.make("Pendulum-v1"), -1.0)

ValueError: Box all low values must be less than or equal to high (some values break this)

The message names neither scale_actions_v0 nor its scale argument, so the
report points at Gymnasium rather than at the wrapper that built the space.

The bounds are now ordered with an element-wise minimum and maximum, which is
the image of the interval under the scaling. Nothing changes for a positive
scale, where low * scale is already the smaller of the two.

scale	before	after
2.0	Box(-4.0, 4.0)	Box(-4.0, 4.0)
0.5	Box(-1.0, 1.0)	Box(-1.0, 1.0)
0.0	Box(0.0, 0.0)	Box(0.0, 0.0)
-1.0	ValueError	Box(-2.0, 2.0)
-2.5	ValueError	Box(-5.0, 5.0)

The dtype is left to Box to infer exactly as before, so integer action spaces
are unaffected by this change.

Tests

test_scale_action_wrapper_negative_scale in test/aec_mock_test.py, next to
the existing test_scale_action_wrapper. It uses an asymmetric action space,
Box(1.0, 5.0), so the swap is visible: with scale=-2.0 the wrapped space is
Box(-10.0, -2.0), and the action [2, 1, 3] arrives at the environment as
[-4, -2, -6]. It fails on main with the ValueError above and passes here.

The existing test only covers positive factors — 2, 0.5 and 0.3 — which is why
this went unnoticed.

Full suite locally: 106 passed against 105 on main, the difference being this
test; the one failure and six collection errors are identical on both sides and
come from optional dependencies missing in my environment. pre-commit run is
clean on both files.

Type of change

• Bug fix (non-breaking change which fixes an issue)

Checklist

• I have run the pre-commit checks with pre-commit run --all-files
• I have added tests that prove my fix is effective