Add configuration-based mapping generator with 4 registration approaches

[davidkallesen]

Summary

Adds a new MappingConfigurationGenerator that enables mapping 3rd-party types without requiring attributes on source types.
Introduces four complementary mapping approaches: mapper class pattern, assembly-level [MapTypes], class-level [MapTypes], and
inline MappingBuilder.Configure(). Also includes performance optimizations across all generators, shared helper extraction,
comprehensive test coverage, and documentation migration to GitHub wiki.

Changes

✨ Features

• Add MappingConfigurationGenerator with mapper class pattern ([MappingConfiguration] + partial methods) for full-control
  3rd-party type mapping
• Add assembly-level and class-level [MapTypes] shorthand for simple mapping declarations
• Add inline MappingBuilder.Configure() / AddMappings() registration with compile-time lambda parsing
• Add enum auto-detection for configuration-based mappings (automatic switch expression generation)
• Add new annotations: MappingConfigurationAttribute, MapConfigPropertyAttribute, MapConfigIgnoreAttribute,
  MapConfigOptionsAttribute, MapTypesAttribute, MappingBuilder
• Add diagnostics ATCMCF001-014, ATCMAP005-006, ATCMAP010-011, ATCENUM006 for configuration mapping validation
• Add MappingOnlyConfiguration sample (CRM external type mapping scenario)
• Add MappingCombinedConfiguration sample (mixed attribute + config + inline mapping)

⚡ Performance

• Migrate DependencyRegistration, OptionsBinding, and EnumMapping generators to ForAttributeWithMetadataName for optimal
  incremental caching
• Replace ToDisplayString() attribute comparisons with MetadataName checks across all 6 generators
• Pre-compile regex patterns in FilterRules and use HashSet for interface exclusion
• Fix string allocation in PropertyNameUtility using range operator
• Add symbol-based HashSet<string> deduplication for partial class handling across all generators

♻️ Refactoring

• Extract shared MappingTypeAnalyzer (9 duplicate methods consolidated from ObjectMapping/MappingConfiguration)
• Extract TypeNameSanitizer for safe generic type name handling in generated identifiers
• Extract shared EnumMappingHelper for enum mapping code generation pipeline

✅ Tests

• Add comprehensive MappingConfiguration test suite (12 test files: basic, property, enum, conflict, advanced, diagnostic, edge
  case, assembly, class-level, inline, error tests)
• Add extended EnumMapping tests (flags, special cases, bidirectional)
• Add DependencyRegistration runtime filter and decorator tests
• Add ObjectMapping error handling and UpdateTarget tests
• Add AnnotationConstants Atc-specific attribute tests
• Add integration tests that verify all sample projects build successfully

📝 Documentation

• Migrate all 18 docs/*.md files to GitHub wiki
• Update README.md to reference wiki instead of docs/
• Update CLAUDE.md with MappingConfiguration generator documentation

🔧 Configuration

• Add sample .editorconfig for sample projects
• Update Directory.Build.props and project references for new sample projects