Remove usingnamespace usage

[hazeycode]

No description provided.

[Copilot]

Pull Request Overview

This PR removes the usage of the deprecated usingnamespace feature in Zig by replacing it with explicit method declarations. The change improves code clarity and follows modern Zig best practices by making the interface methods explicitly visible rather than imported through namespace inclusion.

Key changes:

• Renamed ShapeFunctions to ShapeInterface and moved ConstraintFunctions to ConstraintInterface
• Replaced usingnamespace declarations with explicit pub const method assignments
• Fixed a bug in the calculateLocalInertia method signature

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