Sphere entity and Spherical Sliding Interfaces

[shreyas-flex]

• Adds Sphere entity and support for spherical sliding interfaces in RotationVolume.
• Makes AxisymmetricRefinementBase spacing_* members optional, validation of presence occurs on construction of inherited classes (AxisymmetricRefinement, RotationVolume). This is because Sphere only needs one spacing for construction.
• Adds translation for sphere sliding interfaces in the required style of Flynn360.

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Note

Medium Risk
Adds a new volume primitive and extends RotationVolume translation/validation paths; risk is mainly incorrect meshing JSON output or overly-permissive/strict validation for beta vs legacy meshers.

Overview
Adds a new Sphere volume primitive (exported publicly and materialized via ENTITY_TYPE_MAP) with coordinate-system transformation support, and refactors uniform-scale validation into a shared helper used by Box/Cylinder/AxisymmetricBody/Sphere.

Extends RotationVolume to accept Sphere (including as enclosed_entities) and introduces entity-type-specific spacing validation (Sphere requires only spacing_circumferential; cylinders/axisymmetric bodies still require all three), while keeping Sphere usage restricted to the beta mesher.

Updates volume-meshing translation to emit spherical sliding-interface JSON (type: Sphere, radius, axisOfRotation, center, and maxEdgeLength) and to include Sphere enclosed-object references, with comprehensive new tests covering validation, transformation, entity creation, and translation.

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