`Square(x)` with a zero straddling range bypasses the `divide` zero denominator guard

Start at the Square range calculation and the divide denominator safety check, then trace the model-building path used by the Python example. Add a regression test for an integer range crossing zero and verify that dividing by Square(x) raises ValueError at model-build time rather than producing inf at runtime.

Summary

When a decision variable x has a range that crosses zero (e.g. lower_bound=-3, upper_bound=2),
Square(x) incorrectly reports that its minimum value is positive.
This fools the divide operator's safety check into accepting it as a denominator,
even though Square(x) can actually be zero (when x = 0).
The model builds without error, but at runtime the division silently returns inf.

Expected behaviour

x = model.integer(lower_bound=-3, upper_bound=2)  # range includes 0
model.constant(10) / Square(x)
# Should raise ValueError — Square(x) can be 0

divide documents that it raises ValueError if the denominator can ever be zero.
Since x can be 0, Square(x) can be 0, so a ValueError should be raised at model-build time.

Actual behaviour

No error is raised at model-build time. When x = 0 during solving, the result is inf with no warning.

from dwave.optimization.model import Model
from dwave.optimization.symbols import Square

model = Model()
x = model.integer(lower_bound=-3, upper_bound=2)
sq = Square(x)
ratio = model.constant(10) / sq  # ← no error raised (should raise)

with model.lock():
    model.states.resize(1)
    x.set_state(0, 0)
    print(ratio.state(0))  # prints: [inf]  ← silent wrong result

Workaround

Avoid using Square(x) as a divisor when x can be zero.
Either constrain the variable to be strictly positive/negative before squaring,
or use safe_divide if zero-denominator should map to zero rather than inf.

# Option 1: restrict x away from zero first
x = model.integer(lower_bound=1, upper_bound=5)   # strictly positive
model.constant(10) / Square(x)                    # safe

# Option 2: use safe_divide (returns 0 on division by zero)
from dwave.optimization.mathematical import safe_divide
safe_divide(model.constant(10), Square(x))