Move _is_multiple_of_pi to tool.Cad

Pure-math parallelism check (value ≡ 0 mod π within VTX_PRECISION)
that lived as a module-private helper in mep.py belongs next to
tool.Cad.is_x — same comparator family, no MEP-specific knowledge.
Other features with rotation-difference checks (wall fillet, roof
slope, railing terminus) now have a sanctioned spelling.

Generated with the assistance of an AI coding tool.

src/bonsai/bonsai/bim/module/model/mep.py

@@ -49,11 +49,6 @@ from bonsai.tool.cad import VTX_PRECISION
 V = lambda *x: Vector([float(i) for i in x])
 
 
-def _is_multiple_of_pi(value: float) -> bool:
-    n = round(value / pi)
-    return tool.Cad.is_x(abs(value - n * pi), 0)
-
-
 def _segment_port(segment, at_segment_start: bool):
     port_key = "start_port" if at_segment_start else "end_port"
     return MEPGenerator.get_segment_data(segment).get(port_key)
@@ -1072,7 +1067,7 @@ class MEPAddTransition(bpy.types.Operator, tool.Ifc.Operator):
             start_object.matrix_world.to_quaternion().rotation_difference(end_object_rotation).to_euler().z
         )
 
-        if not _is_multiple_of_pi(rotation_difference_z):
+        if not tool.Cad.is_multiple_of_pi(rotation_difference_z):
             self.report(
                 {"ERROR"},
                 "There is some rotation difference between profiles by local Z axis: "
@@ -1313,7 +1308,7 @@ class MEPAddBend(bpy.types.Operator, tool.Ifc.Operator):
                 start_object.matrix_world.to_quaternion().rotation_difference(end_object_rotation).to_euler()
             )
 
-            if not _is_multiple_of_pi(rotation_difference.z):
+            if not tool.Cad.is_multiple_of_pi(rotation_difference.z):
                 error_msg = (
                     "There is some rotation difference between profiles by local Z axis: "
                     f"{round(degrees(rotation_difference.z))} deg, adding a bend is not possible."

src/bonsai/bonsai/tool/cad.py

@@ -177,6 +177,14 @@ class Cad:
             return False
         return (x + tolerance) > value > (x - tolerance)
 
+    @classmethod
+    def is_multiple_of_pi(cls, value: float) -> bool:
+        """True when ``value`` is an integer multiple of π within tolerance —
+        the parallelism / anti-parallelism check rotation-difference logic
+        reaches for (segments aligned modulo a 180° flip)."""
+        n = round(value / math.pi)
+        return cls.is_x(abs(value - n * math.pi), 0)
+
     @classmethod
     def normalise_angle(cls, angle: float) -> float:
         """Normalise an angle between -179 and 180"""