Add static extensions support for convenient 'using static' directive usage

[konard]

Summary

• Added Platform.Exceptions.Static.EnsureStatic with static methods for argument validation
• Added Platform.Exceptions.Static.ThrowStatic with static methods for exception throwing
• Created comprehensive tests demonstrating static usage patterns
• Added example code showing traditional vs static extension usage patterns

Problem Solved

Issue #25 requested "Static extensions support in the programming language". This implementation allows developers to use C#'s using static directive for more convenient and cleaner exception handling syntax.

Usage Comparison

Before (traditional extension methods):

using Platform.Exceptions;

// Traditional usage
Ensure.Always.ArgumentNotNull(parameter, nameof(parameter));
Throw.A.NotSupportedException();

After (with static extensions):

using static Platform.Exceptions.Static.EnsureStatic;
using static Platform.Exceptions.Static.ThrowStatic;

// Cleaner static usage
ArgumentNotNull(parameter, nameof(parameter));
NotSupportedException();

Features Added

EnsureStatic class provides:

• ArgumentNotNull<T>() - validates arguments are not null
• ArgumentMeetsCriteria<T>() - validates arguments meet custom criteria

ThrowStatic class provides:

• NotSupportedException() - throws NotSupportedException
• NotImplementedException() - throws NotImplementedException
• ArgumentNullException() - throws ArgumentNullException
• ArgumentException() - throws ArgumentException
• Return variants for use in expression contexts

Test plan

• All existing tests continue to pass
• New comprehensive test suite for static methods
• Build succeeds without errors
• Examples demonstrate usage patterns
• Maintains backward compatibility with existing API

🤖 Generated with Claude Code

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Resolves #25