Force NumPy 2 legacy formatting mode for numbers

As a consequence of [NEP
51](https://numpy.org/neps/nep-0051-scalar-representation.html#nep51),
the string representation of scalar numbers changed in NumPy 2 to
include type information. This affected printing Cirq circuit
diagrams: instead seeing numbers like 1.5, you would see
`np.float64(1.5)` and similar.

The simplest solution turned out to wrap relevant parts of the Cirq
code with the context manager form of
[`np.printoptions()`](https://numpy.org/doc/stable/reference/generated/numpy.set_printoptions.html#numpy-set-printoptions),
and use that to set legacy mode '1.25' to get the same string formats
as in NumPy 1.x.

cirq-core/cirq/_compat.py

@@ -192,7 +192,8 @@ def _print(self, expr, **kwargs):
     if hasattr(value, "__qualname__"):
         return f"{value.__module__}.{value.__qualname__}"
 
-    return repr(value)
+    with np.printoptions(legacy='1.25'):
+        return repr(value)
 
 
 def dataclass_repr(value: Any, namespace: str = 'cirq') -> str:

cirq-core/cirq/ops/fsim_gate.py

@@ -196,9 +196,10 @@ def _decompose_(self, qubits) -> Iterator['cirq.OP_TREE']:
         yield cirq.CZ(a, b) ** (-self.phi / np.pi)
 
     def _circuit_diagram_info_(self, args: 'cirq.CircuitDiagramInfoArgs') -> Tuple[str, ...]:
-        t = args.format_radians(self.theta)
-        p = args.format_radians(self.phi)
-        return f'FSim({t}, {p})', f'FSim({t}, {p})'
+        with np.printoptions(legacy='1.25'):
+            t = args.format_radians(self.theta)
+            p = args.format_radians(self.phi)
+            return f'FSim({t}, {p})', f'FSim({t}, {p})'
 
     def __pow__(self, power) -> 'FSimGate':
         return FSimGate(cirq.mul(self.theta, power), cirq.mul(self.phi, power))
@@ -476,15 +477,16 @@ def to_exponent(angle_rads: 'cirq.TParamVal') -> 'cirq.TParamVal':
         yield cirq.Z(q1) ** to_exponent(after[1])
 
     def _circuit_diagram_info_(self, args: 'cirq.CircuitDiagramInfoArgs') -> Tuple[str, ...]:
-        theta = args.format_radians(self.theta)
-        zeta = args.format_radians(self.zeta)
-        chi = args.format_radians(self.chi)
-        gamma = args.format_radians(self.gamma)
-        phi = args.format_radians(self.phi)
-        return (
-            f'PhFSim({theta}, {zeta}, {chi}, {gamma}, {phi})',
-            f'PhFSim({theta}, {zeta}, {chi}, {gamma}, {phi})',
-        )
+        with np.printoptions(legacy='1.25'):
+            theta = args.format_radians(self.theta)
+            zeta = args.format_radians(self.zeta)
+            chi = args.format_radians(self.chi)
+            gamma = args.format_radians(self.gamma)
+            phi = args.format_radians(self.phi)
+            return (
+                f'PhFSim({theta}, {zeta}, {chi}, {gamma}, {phi})',
+                f'PhFSim({theta}, {zeta}, {chi}, {gamma}, {phi})',
+            )
 
     def __repr__(self) -> str:
         theta = proper_repr(self.theta)

cirq-core/cirq/protocols/circuit_diagram_info_protocol.py

@@ -243,13 +243,14 @@ def __repr__(self) -> str:
         )
 
     def format_real(self, val: Union[sympy.Basic, int, float]) -> str:
-        if isinstance(val, sympy.Basic):
-            return str(val)
-        if val == int(val):
-            return str(int(val))
-        if self.precision is None:
-            return str(val)
-        return f'{float(val):.{self.precision}}'
+        with np.printoptions(legacy='1.25'):
+            if isinstance(val, sympy.Basic):
+                return str(val)
+            if val == int(val):
+                return str(int(val))
+            if self.precision is None:
+                return str(val)
+            return f'{float(val):.{self.precision}}'
 
     def format_complex(self, val: Union[sympy.Basic, int, float, 'cirq.TParamValComplex']) -> str:
         if isinstance(val, sympy.Basic):