[🤖] Add ^ Postfix Operator for Suffix String Matching

[Tavernari]

Summary

This PR introduces the postfix ^ operator to the StringContainsOperators library, enabling suffix string
matching functionality. This complements the existing prefix ^ operator and extends the library's capabilities
for expressive string search patterns.

Motivation

The StringContainsOperators library already provides elegant prefix matching via ^"value". However, there was no
equivalent for suffix matching, requiring developers to fall back to native Swift's hasSuffix() method, which
breaks the fluent, composable pattern established by the library.

Before:

// Inconsistent API - mixing library style with native methods
let result = try text.contains(^"My") && text.hasSuffix("Victor")

After:

// Consistent, fluent API
let result = try text.contains(^"My" && "Victor"^)

What Changed

New Files

• Sources/StringContainsOperators/SearchStrategies/SuffixSearchStrategy.swift
  • Implements suffix matching using String.hasSuffix()
  • Follows the existing strategy pattern architecture

Modified Files

1. Sources/StringContainsOperators/StringContainsOperators.swift

• Added postfix operator ^ declaration
• Added .suffix(StringPredicateInputKind) case to StringPredicate enum
• Added two postfix operator overloads:
  • postfix func ^(value: String) -> StringPredicate
  • postfix func ^(predicate: StringPredicate) -> StringPredicate

2. Sources/StringContainsOperators/SearchStrategyMaker.swift

• Added .suffix case to the switch statement
• Returns SuffixSearchStrategy for suffix predicates

3. Tests/StringContainsOperatorsTests/StringContainsOperatorsTests.swift

• Added 8 comprehensive test functions:
  • testSuffixOperator() - Basic functionality
  • testSuffixOperatorWithEmptyString() - Edge cases
  • testSuffixOperatorCombinedWithOr() - OR combinations
  • testSuffixOperatorCombinedWithAnd() - AND combinations
  • testSuffixOperatorWithDiacriticInsensitivity() - Sensitivity behavior
  • testSuffixOperatorInComplexPredicate() - Complex predicates
  • testSuffixOperatorWithCombinedOperators() - Multi-operator combinations
  • testPrefixAndSuffixOperatorsTogether() - Prefix + suffix together

4. README.md

• Added documentation for the suffix operator
• Added usage examples
• Updated the operator reference section

Implementation Details

Architecture
The implementation follows the library's established Strategy Pattern:

Operator: "Victor"^
↓
StringPredicate.suffix(.string("Victor"))
↓
SearchStrategyMaker.make() → SuffixSearchStrategy
↓
SuffixSearchStrategy.evaluate(string:)
↓
String.hasSuffix("Victor")
↓
Bool result

Key Design Decisions

1. **Same Symbol, Different Position**: Using `^` as both prefix and postfix is valid in Swift and provides 
intuitive symmetry:
   - `^"value"` for prefix matching
   - `"value"^` for suffix matching

2. **Consistent Error Handling**: Like the prefix operator, nested predicates with the suffix operator throw 
errors (`.notAvailableToPredicates`). This maintains consistency with the existing implementation.

3. **Case/Diacritic Sensitivity**: The suffix operator is case-sensitive and diacritic-sensitive by default, 
matching `hasSuffix()` behavior. Use `~"value"^` if you need case/diacritic-insensitive suffix matching.

Usage Examples

Basic Suffix Matching
```swift
try "My name is Victor".contains("Victor"^)  // true
try "My name is Victor".contains("George"^)  // false

Combined with Other Operators

// With AND
try "Hello World".contains("World"^ && "Hello")  // true

// With OR
try "The quick brown".contains("fox"^ || "brown"^)  // true

// With negation
try "Hello".contains(!("Goodbye"^))  // true

// Complex nested predicates
try text.contains((^"prefix" && "suffix"^) || ^"another")

Mixed Prefix and Suffix

// Check both ends
try "My name is Victor".contains(^"My" && "Victor"^)  // true

// One or the other
try "The quick brown".contains(^"The" || "fox"^)  // true
                                                                                                                  
Test Coverage

Statistics
- **Total Tests**: 42 (8 new tests added)
- **Success Rate**: 100%
- **Execution Time**: ~0.016s

Test Categories
1. ✅ Basic functionality (match, no match)
2. ✅ Edge cases (empty strings, empty predicates)
3. ✅ Operator combinations (AND, OR)
4. ✅ Complex predicates (nested structures)
5. ✅ Mixed operators (prefix + suffix)
6. ✅ Case/diacritic sensitivity

Example Test
```swift
func testSuffixOperatorInComplexPredicate() throws {
    let text = "The quick brown fox jumps"
    let predicate = "jumps"^ && "brown"
    XCTAssertTrue(try text.contains(predicate))
}

Compatibility

• ✅ Backward Compatible: No breaking changes to existing API
• ✅ Swift Versions: Compatible with Swift 5.7+
• ✅ Platforms: macOS, iOS, tvOS, watchOS (all platforms that support Foundation)

Breaking Changes

None - This is a purely additive change.

Migration Guide

No migration needed. The existing API remains unchanged. Users can start using the new suffix operator
immediately.

Future Enhancements

Potential future improvements could include:

• Regular expression suffix matching via a different operator or combination
• Suffix matching with custom comparison options
• Performance optimizations for large strings with very long suffixes

Notes for Reviewers

1. The implementation mirrors the existing prefix operator architecture
2. All tests pass without modifying existing test cases
3. Documentation is comprehensive with both operator reference and usage examples
4. The same symbol (^) used for both prefix and postfix is intentional and follows Swift's operator overloading
   conventions

Checklist

• Code follows the project's style guidelines
• Tests have been added/updated
• Documentation has been updated
• All tests pass
• No breaking changes introduced
• Change is backward compatible

---

Related Issues: None (this is a new feature)
PR Type: Feature Addition
Impact: Low (additive, no breaking changes)
Risk: Low (well-tested, follows existing patterns)