Fix switched Add/Mul class names in C# arithmetic call files

[Copilot]

AddCall.cs and MulCall.cs had their class contents swapped — each file declared the wrong class and passed the wrong operation name to the base constructor.

Changes

• AddCall.cs: Renamed class/constructor from MulCall → AddCall; corrected base call from "Mul" → "Add"
• MulCall.cs: Renamed class/constructor from AddCall → MulCall; corrected base call from "Add" → "Mul"

Original prompt

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This section details on the original issue you should resolve

<issue_title>fix switched add and mul call in c# files</issue_title>
<issue_description></issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixesfix switched add and mul call in c# files #33

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