Add dedicated IntegerAssertions type with cross-type comparisons

[Copilot]

Integer assertions previously required exact type matching, causing someByte.Should().Equal(0) to fail since 0 is an int. This PR adds a dedicated IntegerAssertions<T> type following the pattern of StringAssertions and ExceptionAssertions.

Changes

• Created IntegerAssertions<T> class: Dedicated assertion type inheriting from ObjectAssertions<T> with where T : struct, IBinaryInteger<T> constraint
• Created IntegerAssertionsChain<T> struct: Enables fluent chaining with .And property
• Moved integer methods: All methods (BeZero, NotBeZero, BePositive, NotBePositive, BeNegative, NotBeNegative) moved from NumericExtensions to IntegerAssertions<T>
• Cross-type Equal/NotEqual methods: Accept any integer type via dual generic parameters (T and TOther), both constrained to struct, IBinaryInteger<T>
• Type conversion: Uses T.CreateChecked(expected) to convert comparison values at assertion time
• Overflow handling:
  • Equal: Throws AssertionException with descriptive message when conversion overflows
  • NotEqual: Succeeds when expected value cannot be represented in target type (values cannot be equal)
• Specific Should() overloads: Added individual overloads for all built-in integer types (byte, sbyte, short, ushort, int, uint, long, ulong, nint, nuint) to route to IntegerAssertions<T>
• Removed NumericExtensions.cs: All functionality moved to the new class

Note: This implementation uses IBinaryInteger<T> constraint to support only integer types, excluding floating-point types (float, double, decimal) which have different mathematical properties.

Example

byte someByte = 42;
someByte.Should().Equal(0);        // Now succeeds (0 is int)
someByte.Should().Equal(42L);      // Works with long
someByte.Should().Equal((short)42); // Works with short
someByte.Should().BePositive().And.NotBeZero(); // Fluent chaining

byte b = 10;
b.Should().Equal(300);     // Throws: "Value should equal 300 but the expected value cannot be represented as "Byte" (overflow)."
b.Should().NotEqual(300);  // Succeeds (cannot equal unrepresentable value)

All 350 tests pass.

Original prompt

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This section details on the original issue you should resolve

<issue_title>Add Dedicated Numeric Type Assertions</issue_title>
<issue_description>The current assertions expect the same type; e.g. someByte.Should().Equal(0) will fail because 0 is not a byte. Add a dedicated NumericAssertions type to prevent this, that is generic over number type. Might need specific ShouldExtensions to instantiate it. Also move the existing numeric extensions into it.</issue_description>

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

• Fixes Add Dedicated Numeric Type Assertions #189

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[MrKWatkins]

I said I wanted a NumericAssertions type, rather than extensions. See StringAssertions or ExceptionAssertions for an example.

[Copilot]

Refactored to use a dedicated NumericAssertions<T> type following the pattern of StringAssertions and ExceptionAssertions. Created specific Should() overloads for all built-in numeric types (byte, sbyte, short, ushort, int, uint, long, ulong, float, double, decimal, nint, nuint) to properly route numeric values to the NumericAssertions<T> class. Commit: bfb4ebf

[MrKWatkins]

Can we rename to IntegerAssertions and use IBinaryInteger for the constraint instead?

[Copilot]

Renamed to IntegerAssertions<T> with IBinaryInteger<T> constraint. This excludes float, double, and decimal types, focusing only on integer types. Removed the Should() overloads for non-integer types and updated all references. Commit: 23dae4b