Implement RBS Record type support

[sinsoku]

Add comprehensive support for RBS Record types ({ key: Type }) in TypeProf with field access, type checking, and error handling capabilities.

Core Implementation

• SigTyRecordNode: Parse and process Record type definitions from RBS
• Record class: New type class with field access and matching support
• Hash integration: Shared builtin support for Hash and Record types
• Type compatibility: Enable Hash-Record interoperability in method calls

Features

• Field access via [] operator (e.g., record[:name] -> String)
• Proper type checking for Record parameters and return values
• Union type support for Record field values
• Graceful error handling for non-existent field access (returns untyped)
• Hash[Symbol, T] to Record type compatibility

Test Coverage

Added 9 comprehensive test files covering:

• Basic Record type usage and type propagation
• Field access and nested Record structures
• Hash-Record type compatibility scenarios
• Error handling for invalid field access
• Optional Record types and empty Records
• Array integration with Record types

Technical Details

Record types are internally represented with a base Hash type to maintain compatibility with Ruby's hash-like access patterns. Field values are properly unified into a union type for the underlying Hash value type.

🤖 Generated with Claude Code

[mame]

Sorry for very late review! TBH I don't fully understand the changes, but I'd like to give it a try. Thank you!