[FEATURE] Add Guards.TryValidateZero<T> ROP guard clause

[dlrivada]

Summary

Add Guards.TryValidateZero<T> to Encina.GuardClauses to provide an ROP-compatible equivalent of .NET 8's ArgumentOutOfRangeException.ThrowIfZero<T>.

Motivation

.NET 8 introduced ArgumentOutOfRangeException.ThrowIfZero<T>() which validates that a value is not zero. This is exception-based and incompatible with Encina's ROP pattern.

Priority: Medium

Use Cases

• Validating divisors before division operations (avoid divide-by-zero in domain logic)
• Validating pricing multipliers (zero multiplier would zero out all prices)
• Validating scaling factors in calculations

Proposed Solution

/// <summary>
/// Validates that a value is not zero.
/// </summary>
public static bool TryValidateZero<T>(
    T value,
    string paramName,
    out EncinaError error,
    string? message = null)
    where T : IComparable<T>

Usage Example

if (!Guards.TryValidateZero(divisor, nameof(divisor), out var error,
    message: "Divisor cannot be zero"))
    return Left<EncinaError, decimal>(error);

Alternatives Considered

1. Use TryValidate(value != 0, ...): Works but loses semantic metadata.
2. Use TryValidatePositive or TryValidateNegative: Only covers half the valid values.

Affected Packages

• Encina.GuardClauses

Test Matrix

Test Type	Required?	Scope	Notes
UnitTests	Required	Zero, positive, negative values, custom messages
GuardTests	Required	Null parameter checks
PropertyTests	Recommended	Invariant: returns false iff value == 0

Implementation Tasks

• Add Guards.TryValidateZero<T> method to Guards.cs
• Add XML documentation with examples
• Add unit tests
• Add guard clause tests
• Add property-based tests
• Update README.md
• Update PublicAPI.Unshipped.txt

Acceptance Criteria

• Method returns false when value equals zero
• Metadata includes guard type (Zero), parameter name, actual value, type
• Custom message support
• Comprehensive unit tests
• XML doc comments

.NET Equivalent

ArgumentOutOfRangeException.ThrowIfZero<T>(T value, string? paramName) (since .NET 8)

Related Issues

Part of ROP guard clause parity with .NET 8-10 built-in throw helpers.