Implement add function for basic arithmetic

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Implement Add Function

Description

Create the core add function that performs addition of two real numbers as specified in the requirements.

Acceptance Criteria

• Implement add(a, b) function that returns the sum of two real numbers
• Function should handle integers, floats, and other numeric types
• Function should be importable from the main arithmetic module
• Include proper type hints and docstring documentation
• Handle edge cases appropriately (infinity, NaN, etc.)

Dependencies

Depends on #2

Files to Create/Modify

• arithmetic/core.py or similar module
• Update arithmetic/__init__.py to export the function

Unit Tests Required

• Test addition of two positive integers
• Test addition of two negative integers
• Test addition of positive and negative integers
• Test addition of two floats
• Test addition of integer and float
• Test addition with zero
• Test addition with very large numbers
• Test edge cases (infinity, NaN)
• Test type validation and error handling
• Test that function is properly importable